nice - marlow (come off at high wycombe), lots of options in the town.
if you want to get further up: j9 bicester head for the town and follow signs to aynho, pub on left, Bure Park Farm is pretty good for sunday lunch.
j11 banbury - you've got the run of the mill toby carvery.
or off at j15, head towards coventry (a46?), take first exit for warwick, turn left towards Hatton, Solihull and The Waterman is about 1.5miles on left. sits on the grand union canal overlooking the hatton locks. (all in all about 3miles from m40)