A final consideration for my choice of supplier was that they should be a member of REAL. This organisation was set up by the Renewable Energy Association to not only establish quality standards but importantly to offer various insurance schemes.
This was important since I have decided to go with a small local company Firegrass Energy Ltd for the installation, because as far as possible I always try to support local businesses. As they are a member of REAL they then pay for a "Deposit and Advance Payment Insurance Scheme" which means that the deposit I need to pay when ordering would be covered by insurance should they 'go bust' before the installation is complete.
With this safeguard and from the very informative and friendly style of Firegrass, and of couse an acceptable price, I placed the order on 26th September, and was pleasantly surprised to receive the REAL insurance ceritificate through the post just a few days later.