Well I gave up
Moral of the story fill in your standard A500 as a 't-jet' not a (135) 

I'm still confused as to the difference between 500 Abarth 't-jet' and 500 Abarth (135) but the t-jet which my car is registered as by the dvla is group 29 and the 135 is group 12, for whatever reason that is. My cheapest quote jumped from £560 with £100 voluntary to £677 £250 voluntary. So the old bank balance has taken more of a kicking than I thought.

Just be aware of this when using money supermarket.

Yeah I read that it was 26 but the guy on the phone was adamant that on the dvla records now its group 29. I'm not sure what the story is but basically the money supermarket system is screwed for A500's. Do it yourself.

Morethan were extremely bad when I rang them, clueless, I guess it depends who you get