check with both the 2 cheaper quotes whether you will get:
1. installation certificate.
2. notification to LABC. this generally entails the spark to be niceic.napit, stroma etc.
IMO, £145 is way too cheap. the £211 sounds in the right price bracket.
Already checked and cheapest guy comes up 100%, established 1999 too. I have no idea how he makes a living at his prices, but that's his lookout