Battery for 97 K11 - how much?

hi all,

I am selling my mrs' K11 on Friday, and just my luck it wouldn't start last night.

I need a new battery, so just want a cheap as chips one but phoned up a few local part firms who want £30+, is this about right?

:( cheers, well i'll have to bite the bullet then. The mrs would be scared to drive it for the week if I picked one up from a scrappy or something.