All products are sold via channels, where you buy in the channel may
determine 1) your status in law re Business or Consumer and 2) Price
and Minimum Quantity, ie, Terms & Conditions. The law makes a very
clear distinction between Trader/Business & Consumer/Retail... would
be interesting to know if the "trade cards" diminish your rights as
implied to B2B buyer in place or B2C re Screwfix "trade", B&Q "trade"
and so on.

Most "trade outlets" whilst often selling to consumer want to apply
trade terms, most consumers buying at trade outlets want trade prices;
an interesting conflict. The trade place usually covers themselves re
"just getting a price off the computer".. followed by 15 minutes with
a calculator... slide rule... gordon brown telephone call... teeth
sucking... wallet weight check... stubble rub... and a sky high
price :-)

A solution if you want quality work is 1) buy the stuff you want
installed yourself 2) define how you want it done or at least the end
result 3) that which you do not inspect or monitor, you do not
control. So a photo of wiring to roofing before, during & after is a
very good idea. Since we lost manufacturing, and underlying cost of
living is so high, we have lost a lot of skilled people in terms of
they move into other areas. Hence £100/hr and £70/hr can buy the
difference between a very experienced tradesman and a complete
imbecile - or no difference whatsoever.