Having this trouble myself. There are ones on ebsy but thinking of trying getting the existing one reset for £25.
http://www.northernautotech.co.uk/airbag.html
When i work out how to get the bugger out, t50 security torx?
This worked a treat after 5 goes.
When counting for the 3 seconds, i noticed a click sound from the car so used that as a guide for when 3 seconds were up.
Also, not sure if this helped.. But.. the last bit, about turning ig on then off for at least 1 second.. I let airbag go out first...