Yes is just compatible and you can add a motor as well. I haven't tested it my self just yet but with track the train should just fit under the bridge.
Track can be expensive a cheap way is just to buy a motorised train with track on a discount. as it cheaper then buying losse parts.
But just buying a single set of straight tracks should be enough for you needs. (for display) if you need a full round you need 3 full sets but you only close the round with flex track.
I bought my self a set 60197 as well as it is on sale quite often (normal euro price 130) but I got it at 94 euro so around 82 pounds. that is very close to 50 pounds for tracks but now extra train and powered up functions. And you can always find a good use for the extra blocks in the set you get 677 blocks for just under 30 pounds / euro difference with a controller and motor and battery box. :)
there are a few manuals on youtube how to upgrade your Hogwarts express train to do this (with some extra red blocks you can do it in the tender also make the tender a bit bigger as it way to small I think)
