Just purchased a new replacement battery for my old tomtom V1. Original battery is marked F62812051, the replacement that I had from ebay is a TM600SL which is approximately a centimetre longer in length. Problem is that it will not fit the battery moulding in on the back of the tomtom.
The seller assures me that this is the only battery available for the v1, so is there any way that this battery can be used in a version 1?

If it won't fit it won't work ;)
The seller sent the wrong one, might be that he has nothing else, but usually a battery does not change it's size.