If you want an hour into St Pancras / Kings Cross / Euston then Leicestershire / Milton Keynes / Bedfordshire become options. You can get fairly big semi-detached houses with gardens in good areas for 300K.
300k is a very tight budget as you’re looking on the edge of London and what is possibly the most affluent area outside London.
I can see that Redhill would be just about doable for a 2-bed house. It’s has excellent train services into London and would be an ok drive to Walton on Thames. Decent primaries but excellent for secondary if you’re either CofE or Catholic.