Can anyone recommend one of these new French restaurants at all? Not
that the OP, having just come from Paris, will really need such a
recommendation... so can anyone recommend a good restaurant offering
traditional British dishes in Kings Cross? I can't immediately think
of one I must admit. I recall there being a decent looking place in
the new Regent's Quarter development just north of Pentonville Road,
but I think it's Spanish.

No idea on KX; but how about a different tack:

a. from Kings Cross take Piccadilly Line to Covent Garden

b. walk through Covent Garden (one of London's popular tourist
destinations) and eat there or nearby: a plethora of cuisines and price
brackets - including, as an exemplar of British cooking, and bearing in
mind the strength of the Euro (spit!!!), http://www.rules.co.uk/ (I can
recommend the Rib of Beef, on the Bone or the Steak, Kidney & Oyster
Pudding). It ain't really the place for a pre-match snack though )

c. then it's a 15 minute walk to Embankment (via Trafalgar Square to
tick it off - though I think it is only worth it for those who
appreciate the history) to catch the Circle; or a 25 minute walk via
Trafalgar Square and Whitehall to see the House of Parliament and
Westminster Abbey before getting the District Line again from
Westminster; or if time is tight Piccadilly Line again from Covent
Garden to Earl's Court and District Line from there?
--
Robin