No need to check in early unless you are taking the Eurostar. First class tickets in the UK come with a club access at the train station, free food, and drinks. Also you can choose a seat assignment in first class. My favorite Country to do first class, worth the expense. If you download the Eurail app, you can look at train times, how many transfers, if you need reservations (it will tell you on the selection). It's nice to able to look at all the available trains and times to help plan your trip. If you buy rail passes, they are good for 11 months, I think. Go on sale around November and sometimes in March, 20% off for first class is worth it. Happy Travels.