What a bloody PITA it was changing the battery yesterday!
Not one YouTube video seemed to show my exact model. Then the tiniest screws in the world were not standard Pozi or Philips..they were teeny weeny start shaped. Not having a small star shaped screwdriver or bit I used brute force and ignorance using a small pozi drive and digging it into the crews. It didn't work on all of them so I tried my long nosed pliers...nope: not enough metal to grip on all of them. For some I ended up using nail pincer-type cutters to grip the metal!
Anyway, I managed in the end and it still worked so we'll see how it holds its charge now. Probably best to gauge that after a few charges/discharges I guess.
If it does the job for 14 quid and we can get a few more years out of it, then it was well worth all the effing and jeffing!