Kitchens are (generally) the second most difficult room after hallways.
Few questions first (well, aren't there always?):
What's your sub-floor? Concrete (and if so, how old? existing DPM?)? Floorboards? Ply/Chipboard? Straight-to joists?
Are you planning on going from the ground up? i.e. will you be fitting a floor to the full area and then building your kitchen on top? Or will you be having the kitchen fitted then have the floor fitted to just beyond the kickboards?
You might want to consider engineered flooring rather than solid - especially in a prone-to-spills, humid, hot'n'cold room like a kitchen.
What kind of finish do you want at the end? Dark? Light?
I'm assuming you'll go with an oak floor of some kind...?
EDIT: Throwing out a figure like £15/sqm + adhesives might lead the OP to believe he might get 40sqm of timber flooring laid for ITRO £600 + a bit for materials, which I'd very much doubt TBH.