I had quite a few problems with my 2 day old Carrera machine. I was helped out by a chap called Davey White who is one of the senior members of staff on the support side.
Stick with it they were really helpful once they got moving.
As always try to getting their help as nicely as you can - I know there are some long waits which wind you up (they did me).
At the same time give your local trading standards a ring - not to report a problem - but just to confirm your right to a refund although if you accept a repair initially I think it reduces your refund options - anyway check with them.
Stick with them if you can I am (touch wood) happy with my machine once it was fixed.