Yes, you can use Eurail pass for most of that. And you can use it for cross-border trains.

In fact, Eurail is great in the UK and Switzerland, because you don’t need reservations, and the normal train tickets are quite expensive.

You’ll need to pay an extra reservation fee on the Eurostar London-Paris. €30 per person. And on Paris-Switzerland (€29, but there are ways to reduce this cost if you take a slower route.)

You will need to buy local tickets between Paris and Marne-la-Vallée (the station for Disneyland), as the pass isn’t valid here. And tit’s not valid on the mountain train from Interlaken (you get a 25% discount).

If I’m reading your itinerary correctly, I count 7 travel days. So you could get a ‘7 days in one month’ pass.

For local transport within cities I would suggest

London: use a contactless credit or debit card on the tube and buses

Paris: you can buy single tickets from the cafe onboard the Eurostar, but if you’re there for a couple of days you’ll probably want to buy a Navigo Card. You can buy this at the ticket office in Gare du Nord, and load it up with credit. You can also use it to pay for the trip to Disney.

Geneva: buy a day ticket from the ticket machines if you need public transport.

Be aware of the 2 mandatory reservations on your route, trains will sell out during the Christmas and New Year period.

Book the Eurostar ASAP. This route is very popular and has a passholder quota (30€ reservation).

Available departures right now for 26th December :

Paris : 15:31, 16:01 and later

Lille : 09:01, 11:04, 13:01, 15:01 and later. You can connect to a TGV : 10-20€ seat reservation extra though.

You can book through eurail.com if available (2€ fee per person per train) or for sure on (4€ fee per order).

TGV Lyria (29€ Paris - Basel) should also be booked soon but there's no quota. 10-20€ to Strasbourg or Mulhouse if you want to save a bit.

Which mean if i bought the Global pass, i also have additional charges if cross to from london to paris and also paris to interlaken ?

How about Swiss Pass, what is your advise ?

The pass = your ticket for most of the trains in Europe.

But for trains with mandatory reservations: usually high-speed, international trains and night trains, you need a seat reservations. For your plans, these trains are Eurostar, TGV (Inoui and Lyria). In order to travel valid you need a valid pass + a seat reservation. Without the seat reservation, you won’t be able to board or fined big time.

Please get your Eurostar seat reservations as soon as possible.

Personally I think a Swiss pass won’t be worht it for you. You’ll travelling in quite a busy (so expensive period) for all other trains. 

Yes I also think the Eurail Global Pass is the better choice over the Swiss Travel Pass.

Looking at Eurostar tickets for 26th December :

- London - Paris : 150-250€ !

- London - Lille : 110-150€ !

It will be a very very busy day so as suggested book this train soon.

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

But can i travel in Switzerland Geneva and Interlaken for my Eurail ?

Eurail is valid for trains in most of Switzerland - including getting to Interlaken.

It’s not valid on local buses/ trams etc in the cities.

It’s not valid on the railway from Interlaken to Grindelwald/ Lauterbrunnen/ Jungfrau, but it gives you a 25% discount on the fare.

The Swiss Travel Pass is valid in cities, and from Interlaken to Grindelwald (but not higher than that), but I agree that it’s not a good pass for your journey.

Tickets in cities aren't more expensive than elsewhere either. 3-4 CHF for a 1h ticket depending on the distance.

Grindelwald/Wengen - Jungfraujoch costs the same whether you have the Eurail Pass or Swiss Travel Pass (25% discount only) : 160 CHF.

It is very expensive and unless the weather is really good there's no need to go. You shouldn't buy tickets in advance anyway, they can't sell out.

To make Chamonix a nice day trip from Geneva take this route :

- IR90 Geneva - Martigny

- R Martigny - Vallorcine

- TER Vallorcine - Chamonix

And for the return :

- TER Chamonix - St-Gervais

- TER/SL3 St-Gervais - Geneva (sometimes extra change in Annemasse)

Thank you thibcabe and Ralderton, your info lots of help to me