I have just had one of my keys "done" by Martin and a fine job it was.
Both my original keys had problems with wear so I was going to sort both out.
I sent the worst to Martin who re-soldered the battery tray and changed the switches.
I then bought a key complete off ebay, I bought two actually as I needed two. The first cost me just over £30 and the second just under £8. Depends who is looking at the time I suppose.
On the first key, the one re-vamped by Martin, I kept the blade and the electronic bit, the rest was crap. I found that you needed a new or nearly new key to make sure the little towers of rubber that pushed onto the switches inside the key were in good condition - this I found to be important.
As well as looking for a fob with 3 buttons you need to confirm with the seller it is the fob with the led light lighting up when you push a button.
So with re-vamped insides and nearly new outsides plus a new battery my first key is as good as new.
I intended doing the same thing with my second key but I found that when a good outside bit, with good rubber towers inside was joined together with the old insides and a decent, not new, battery that too worked fine.
I would like to state here and now that Martin is a wonderful person and turns around the work very quick indeed. I would recommend his service to everyone. He asks for a measley £7.50 for the job. I sent him a tenner and I think that is cheap at twice the price.
To people who's fobs are playing up, watch ebay and get yourself a spare for when you eventually need it. Afterall, these things are only going to get more scarce and expensive.