Good idea to travel ! I'll try to share some advice down below.

Europe is very diverse. This is no different when it comes to trains. There are 2 main policies :

- France, Spain and Italy + some cross-border routes : mandatory reservations on fast/high-speed trains (extra costs). This restricts your flexibility as trains can sell out weeks in advance around Christmas & New Year, more below.

- Germany, Austria and most of Europe : optional reservations and you're always allowed to board. As you're travelling alone you shouldn't have an issue finding a seat.

Regional trains do not have reservations. Simply log the train to the app before boarding (as usual) and hop on. 

Eurostar is unlike any other European train : you must arrive 45-60 min in advance to clear security and passport controls. For all other trains you can arrive 10 min in advance without issues (maybe 15 min if it's a big station)

I'd get a 10 days within 2 months pass as it is on sale until tonight (25% discount). 1st class doesn't cost much more if you wish, this should increase your chances to find a seat/a reservation.

1st class optional reservations are free in Germany, Austria, Czechia through oebb.at (Austrian Railways) -> add Eurail as a discount and select one-way tickets. Since they're free I'd always make one for piece of mind (even if only an hour before departure).

I'd recommend reading these 2 links :

https://www.seat61.com/how-to-use-a-eurail-pass.htm

https://www.seat61.com/interrail-and-eurail-reservations.htm

Questions welcome of course.

Last thing : make sure you've got a valid passport. It must be valid 6 months after your return date.

Now this was general advice. About your trip in particular :

There's only one issue : getting in and out of the UK. Crossing the Channel is a bottleneck. Eurostar trains from London to mainland Europe are extremely popular and there's a passholder quota too (exception). Capacity is also limited at London St. Pancras due to extra checks required by Brexit (mainly stamping British passports) : morning trains cannot leave fully loaded because of that.

You must book Eurostar trains ASAP (but the rest of your trip will be more relaxed, don't worry!). Check Eurostar availability here : https://www.b-europe.com/EN/Booking/Pass#TravelWish

I'll make a summary down below. Let's say you wish to leave London for Paris on 27th December.

27th December : trains to Paris all sold out. Trains to Lille-Europe available at 07:04 (1st/2nd class) and 09:01 (1st class only). 30€ 2nd class/38€ 1st class.

From Lille you can easily reach Paris by TGV high-speed train : 10€ mandatory reservation, these trains rarely sell out but book in advance ofc. The 09:01 train is ideal as you can arrive at the station around 8-8:15am. Don't worry, the terminal will be packed but it's always like this : they process people quickly.

Connection example :

- Eurostar London St. Pancras - Lille-Europe 09:01 - 11:26 38€ 1st class (1h time difference)

- head out of the station for a quick visit, lunch break

- TGV Lille-Europe - Paris-Nord 13:03 - 14:32 10€

After Paris I'd head east, let's say on 30th December.

Germany, Switzerland and Austria are great countries for Eurail as you've got full flexibility ! You can literally show up at the station, log the train 30 seconds before boarding and hop on !

If you wish to go to Paris book the TGV high-speed train towards Germany/Switzerland ASAP too (but there's no quota and 1st class sells out later than 2nd).

To end your trip with a fun experience you could consider the Vienna - Brussels/Amsterdam night train. Private or shared compartments are available but you must book ASAP too. You only pay accommodation price on top of the pass (couchette, sleeper). Remember that you save a night accommodation while travelling.

EDIT : looks like availability is quite limited (+ the website doesn't work well at the moment) so it might be better to forget that option. Unless you really want to and I'll have a thorough look when it works !

You should arrive in London on 6th January to make sure you've got enough room before your (likely) morning flight.

Hope I'm not worrying you too much. Honestly as soon as you've left the UK/France things will work out a lot better !

THANK YOU for the reply and insights into the different train systems. I did grab a 10 day 1st class pass, so seems I need to somewhat confirm my itinerary,  such as where to spend NewYears along the way!

I’ll read through your links, and apprecaite any advice to possible 2 week itineraries starting and ending in London

Thank you again

You're welcome ! I updated a little my post above.

I see 3 possible itineraries (but there are more of course) :

- London - Brussels - Amsterdam - Munich - Paris - London

- London - Paris - Munich - maybe Salzburg - Vienna - night train to Amsterdam/Brussels/Paris (where there's availability basically) - London

- London - Paris - Switzerland (spend New Year there) - night train to Amsterdam or daytime trains to Brussels/Amsterdam - London

The night train is not a must but it'd save you a lot of travelling time.

The last option is my favourite : Switzerland is a fabulous country for scenic train journeys. Just one example : https://www.seat61.com/trains-and-routes/bernina-express.htm

Reservations aren't a thing (except on the Glacier Express + panorama carriages of the Bernina Express but there are alternatives) so you can hop on hop off whenever and wherever you want. Trains run at least hourly but usually every 30 min on mainlines.

In December - January while daylight is limited and skies are often grey the Alps are a safe bet with snow and likely sunshine.

Questions welcome. I can especially help on Switzerland as I live there :)

Also look into an open-jaw return for the flight, so you don't have to return to London (or start elsewhere). This isn't necessarily much more expensive than a normal return and saves one Eurostar reservation to/from London, which is hard to get around the holidays.

Ah yes I wasn't sure if you had booked your flight or not.

This would allow to do something like London - Paris - Switzerland - Vienna (or Munich) - flight home

In any case if you must go back to London, the Zurich - Amsterdam night train is available on 3rd or 4th January : 144€ for a private single compartment. It appears expensive but remember that you're travelling 800 km while asleep :)

Then the only direct available Eurostar leaves at 08:45 on 6th January (2nd class only left though). To have more options I'd recommend going to Brussels and change there :

- reservation-free hourly IC train

- margin for passport controls

- Eurostar departures at 10:56, 12:56, 14:52, 16:56, 18:51, 20:22 (both 1st/2nd class available)

Questions welcome as always :)

THANK YOU again for the feedback rvdborgt and thibcabe, Super helpful. Im going to see if I can adjust my return flight so I dont have to fly back from London, to give me a few more options

I’m sure I’ll be back with more Q’s, thanks again!