My favourite at the moment is Petit Pois. The dishes are reasonably priced and not big, so you can a fish course, meart course etc with accompanying wines at a reasonable price. They do a good fixed price lunch menu as well...
I seem to remember they lay on extra trains for the big games at Wembley Stadium station. No doubt we’ll have more info nearer the time. The good news is a major headache has been avoided with the Brighton to London line running normally.
When I’ve done the return journey for Englang games my preferred route is:
Wembley Stadium - Marylebone - Victoria - Brighton
Rationale...fastest route to Marylebone, then either tube or taxi if running late to get the Brighton train. Plus lots of places to go for a post match meal and drinks...