Sadly you were right Rick, tried new batteries, no luck. It's now turned into a good looking bit of decoration. Already ordered another XA (regular this time, with proper rangefinder) on eBay as I really thought of it as being the ultimate take-everywhere compact 35mm... Shame it's not all mechanical, wouldn't have had a problem like this if that were the case.
Luckily have another camera or two (or more) so need to worry about getting something digital. ;-)