I bought one of these shown in the link. I must admit I havent used it yet even though I bought a Peugeot keypad from Ebay for £2 to practice on. You have to unsolder the surface mount chip.

The company was amongst the worst I have ever dealt with, not replying to my emails and not sending a VAT invoice. If I ever get round to using it I'll let you know if it works!

Regards

Steve