You can use in your home country only on 2 days (Outbound/Inbound Rule). 

Your home country is where you live, how it works for students that are on an exchange program, I don’t know. Great Britain or The Netherlands. 

In the Netherlands you're required to register with the local authorities, so you should be able to demonstrate that you live there.

From the way you describe your plans it would seem you can declare your country of residence either way as you would only travel in the UK on 2 of the days and in the Netherlands for 2 days.

If you have official documentation in your student address for your stay in Rotterdam then that would suffice if challenged, but the general consensus is you are unlikely to be challenged for any proof of residency whilst travelling. The App does the policing based on your original order, only allowing 2 days with any travel in your “home” country.

You would though need to use your Netherlands address if you planned to use your fourth day to get from Leeds to Durham.

OOI Paris to Leeds is easy in a day, as would Durham to Rotterdam.

Enjoy your visit home.

IF you really have found an ´official´dig here in Rtm, then you MUST register with authority-as otherwise you will be expelled after some time. You will then get some official form to state you live here. This is a bit unusual for Brits, but common anywhere else in EUR and known to all. It should also have been clearly stated in all the documentation you get from uni.

IF you claim GB to be home, then you also run a chance that some inspectors challenge it, as its officially for 1 trip OUT and 1 IN-and GB is about the only country where there have been reports this is ineed checked-due to sometimes even train tix in GB costing more as a 4-day pass.

Strange you should suggest UK inspectors would be in any way interested in whether you are a Brit trying it on or a Brit genuinely living abroad. All I have experienced is collectors who visually check the pass for validity (they can’t read the QR code) for that train. One even admitted he knew very little other than to check it like a normal paper ticket - Train start and finish, date and time. 

In this case (4 days pass) it is even less of a problem. 

I do though agree that turn up and go prices for the UK can be eye watering, especially at peak times.

Thalys and Eurostar supplements make this trip less attractive I believe. 

For all holidays I, like many, work on simple economics combined with personal choices when planning.

I take all costs and add them up then combine them with the emotional and social factors such as time travelling, comfort, stress and “adventure” to make my mind up.

Interrail makes its costs clear and reservations are a part of those costs,

There is no doubt that reservation costs on E*. Thalys and SNCF trains are a significant factor but if you were to cost a trip from my home in Yorkshire to Brussels by train for example, it could easily cost £200 single and takes about 6 to 8 hours. A pass costs about £30 to £50 per travel day. Add the E* fee of £30 and journey costs £60 pp.

The cheapest buy ahead E* for next April is £65 pp and to get to London before 1200 to connect with a decent E* will be about £100.  Neither of these are exchangeable or refundable without extra fees.

It is correct that E* has no res free competitors so you could consider ferries or flights but you cannot compete with 2 hours city to city.

So yes the res fees are significant but the journey is still attractive compared to the alternatives.