Thanks all, yes unfortunately I haven't got a garage so the car's on the road, hence my striding forth optimistically and removing the battery. There are some cables to connect permanently but obviously can't use them.
I'll get the mechanic to check for reasons for battery drain when I take it.
I know, Halfords isn't that great, but I wanted to charge the battery up as I wasn't in a position to drive it round for an hour or so, and Halfords is just round the corner from me.
Is there a good one you can recommend or a website with good bits on?
I wish I'd found this forum before I tried rogue-stylee to fix my car (I've been known to take computers apart before but never the car, computers are so easy, cars very tricky!