Thank you Fred and D. Was tricky as don't have socket with extension but you can just about do it with a simple spanner and lots of patience!
Gus
December 2009
After changing the battery you will probably need the radio code and may have to reset the remote locking fobs (turn ignition until dash lights come on, press the lock button on the fob, doors should lock then unlock ).
fred
December 2009
10 mm spanner to disconect the terminals earth one first 13mm socket with long extention for the clamp. wiggle it out the hole refit new battery fit clamp refit terminals live first