England FlexiPass

Thank you for the info on the necessity of validation at the Heathrow counter before using the passes. I purchased them from VisitBritainShop.com. Oh good grief, I just saw that under 'Class' (in fine print) it says '1' So sorry for the trouble, but thank you for that information on Heathrow and the pass. No kidding, I'd looked 'everywhere' on those tickets and couldn't find First Class. Grr. Thanks.

FYI to save you looking the services from St Pancras to Canterbury West are standard class only (although if connecting at Ashford that train might well have). Southeastern also doesn't offer seat reservations.

Thank you very much SteveB and Marco. Appreciate the info.

Which other journeys are you making? We could then give you an idea if reservations are needed and/or possible.

Generally first class is only really worthwhile on journeys more than a couple of hours long. Some trains on shorter journeys or commuter lines might just have a few seats in a small first class section, whose only one advantage is that they're slightly bigger. On longer journeys, though, first class means all sorts of good stuff like free food and at seat meal service.

We used First Class Flexi-passes in 2015 and they were great. One of the train trips was from Kings Cross to York and on to Durham, on Virgin, and it was nice to have plenty of room and food! So the trips we'll be taking by train are from Heathrow Express to London; London to Canterbury to Dover; London to York to Durham; Oxford to London (a late train).

Interestingly, yesterday when I contacted the vendor where I purchased the First Class Flexi-passes, they wrote back with this:
"It is actually not necessary to book seats with a Britrail Pass. It is only recommended on very busy lines and needs to be done directly at the station, it costs 10£."
Really??? £10 to reserve seats on a train I've already purchased tickets for??

Well there won't be any kind of additional benefits on the Oxford to London Paddington train as there are no buffet services left on them unless possibly it has come from beyond Oxford, eg Hereford. If it is a train to Marylebone then these are standard class only.

As for the reservation fee this sounds like what Britrail agents charges online. Reservation is free if done at a station, although the need to do so first class outside busy times is limited.

Right. Ridiculous price for reservations. But we'll have time once in country to make the reservations from London to Durham, and free, or nearly so, if I remember correctly. Renting a car in York and will drive from there to Oxford after visiting both Durham and York. Thanks.

While reservations do cost money in other countries, they should be free with a BritRail England pass, up to (I think) 24 hours before the scheduled train departure.

You may not be aware, but there's no connection between Britrail (which issues tourist Rail passes that can only be bought by foreign visitors) and Britain's train operating companies. The TOCs honour the passes but I don't know what the financial arrangements are between Britrail and the various train operating companies. But I thought it would be useful for you to understand that the passes are not issued by the train operators. And that might explain why some of them will charge for reservations.

Reservations aren't essential - all the long-distance trains will usually have at least one completely unreserved carriage (often carriage U) and there will be some unreserved seats in the other carriages too. But if you're travelling at a busy time you will find there's a mad rush at the station to get on the train and grab an unreserved seats so you may want them as back-up. If you think British people are polite, just wait till you see a rush-hour train.

Britrail was an old brand originally started by British Rail and was
given to ATOC when BR was broken up and privatised.

I stand corrected!

Anyway, it's a minefield.

Thanks everyone for your very helpful information. It looks like the only seats I'll need to reserve are on Virgin, London to Durham and then Great Western, Oxford to London.

Only some trains from Oxford to Paddington have reservable seats - those operated by HSTs. Those operated by Turbos do not. The latter only have a very small first class section at one end (or at one end of each unit if they are being run in multiple).