buying a ticket on match day

I won't know if I can go until tomorrow. Online ticket price is 18 quid plus 2 quid booking. Will the 18 pound price be the same if I buy tomorrow or does it jump up ridiculously to 30 quid or something?

I think that would £ 21 on the day but no booking fee if you get it from the ticket office.

Actually it's £24 on the day. Well in the Canton anyway.

Cheers chaps