You might also be able to get a general electronics repair shop to do it for you, for around £20-£30 including cells, or cheaper if you supply them.

Not many of these places around any more though, at least in the UK. And many of those that are won't do anything more adventurous than changing an iPhone battery, especially those nasty little corner shop thingies. If you go in and they don't at least have an oscilloscope, multimeters and soldering irons in the back, you generally don't even have to ask if they'll do it - they won't.

It's a shame, as a lot of apparently dead-forever electronics are easily fixed, often by just replacing one simple cheap component. I recently fixed an old monitor I thought was dead; turns out the on switch was just stuck. Opened it, oiled the switch, good as new. There's no way I'd have found a repair shop willing to try to fix a monitor - the vast majority of people just buy a new one.