Hi Jack

When I first looked at your post I thought quote 1 was too cheap ( are the company making any profit?) Quotation 2 too expensive and quote 3 seemed middle of the road and around the asking price of a middle of the road quotation for the equipment supplied.

I then had a look at the data sheets for quotation 1 and the kit seems fine.

Quotation 1 Italian panels and Chinese inverter.
Quotation 2 Chinese panels and inverter.
Quotation 3 Chinese panels and inverter.

The Chinese make 80% of the panels sold around the world and their inverters on paper are excellent.

I have never used any of the inverters so cannot tell you long term reliability but on paper there is not a lot between them.

If you do not mind a blue poly panel, the first quotation is best value for money.

You also need to look at the companies involved in the installation this is just as important as the kit involved.

You can always contact Stuart the owner of this website and he can put you in touch with a good reputable company near to you.