Good & affordable near 94-99 High Holborn
I would say if you're able to do just a little walking down towards Covent Garden you'll be in much better shape.
Great Queen Street is getting good reviews - it's certainly walkable from Holborn but I can't comment on prices as I haven't been yet.
There are also some affordable options near Seven Dials (Rock and Sole Plaice on Endell St., Food For Thought on Neal St. and Belgo on Earlham St.). There's also a nice pub called The Old Crown on New Oxford St that does a decent lunch, nothing too fancy but not cookie cutter pub food either. I am not sure if they serve dinner, but it's worth a look.