Cheers Colin, much appreciated.

I still don't get it though - If I pay someone to fit my "power
system", it is 5%, if I buy it from the same people and fit it myself,
it is 17.5% - mmm - anyone would think the government doesn't want
renewable energy. When I eventually get round to doing mine, I will
have to have a chat with my accountant. I will also contact clearskies
and register my complaint at their being DIYist. There must be ways for
them to prevent fraud. If I buy the kit from a registered supplier and
they certify this then surely that should be enough.

I'm allergic to tradesmen hence the question about costs.

Thanks again,

Alan.