Jewson is owned by Saint-Gobian which is the umbrella for some other's as well
http://www.jewson.co.uk/working-with-you/supply-chain-partnerships/jewson-and-saint-gobain/
Add Wolsely (PLumb Center) to this as well which was bought out by Saint-Gobian in 2011
Interestingly
Wickes is owned by Travis perkins
AND
Kingfisher PLC owns B&Q, Superdrug (various French DIY outlets) and
Screwfix
I avoid Jewson (& TP) like the plague. Over priced and generally rude staff IMO. You can't see prices online unless you log into your account. WTF? Is it a builders merchant or some exclusive club?
I've found this true of most large merchants, they generally see themselves above dealing with everyday public, they want mainly larger firms, large orders, as to them it's less hassle.
I use an independant timber merchant for materials and get a 10% discount despite most of it being for myself. The quality of timber is superior to B&Q,
Wickes at a cheaper price and on par with the big merchants.
I'd say find an independant if you want to pay nearer trade price as an avid DIYer, get a mate with a building company and get yourself a trade card, they will welcome the business and appreciate it. Otherwise you're lumbered in with all the 'civvies' crowding the checkouts on a saturday/sunday with gaudy guff that the missus wants for the house.