I cannot see the fuss here, if it is B&Q, Wickes, Homebase, Jewson, Travis perkins or anyone else for that matter. They are not timber suppliers so the quality they supply is cheap and cheerful or with a heavy mark up. I have supplied timber in the past to many of these retailers, they have at least 100% markup and purchase from the large saw mills who cut/mould and shrinkrap the packs.
I know for a fact that in Central Scotland the same facing/architraves are of the same line machine that supplies both B&Q, etc and the Joinery/Housebuilders in Scotland and are run at the same time just packed different. So to state all materials from B&Q are low quality is missing the point. B&Q buy cheap from national suppliers at bulk discount. All suppliers do and, they like you, need to purchase materials and must go to a timber supplier, so why do you not do the same, I used to supply a national chain with Roof Trusses for example. You should travel to a supplier that will meet your needs or get delivered if you purchase enough or drop off it of if delivering in your area. 5ths/Unsorted/Sorted or Joinery Grade you must go to a timber supplier who has equipment on his premises and will cut/mould to order, and more importantly a kiln. It would be hard to find a tradesman now who can tell the difference himself between the grades or what knots or amount/by length, as they seem to go to Jewson, go see where they store there timber in the yards so no matter what grade is put in the storage can play a part, I do not single out Jewson, Travis/Wickes/Homebase, etc ,etc they are just middle men.
The fact is timber purchased must be picked to do the role it is planned for and selected by you accordingly. As most on here seem to be DIY or hobbyist it is more important you purchase correctly and local timber suppliers should give advice easily it is in their interest for repeat custom. It must meet your moisture needs (or meet the environment it is to go into) and it must be checked on delivery or prior if uplifting. I return whole packs for moisture (which I monitor)/Packaging missing (part of my purchase contract it must be kept dry/stored dry) or not meeting the standard I purchased (can happen even to me some oink slipping in a pack here from the key side not knowing one pack from another or there thinking I will not monitor, happens once by a supplier there is never a second).
Of late it seems harder to buy bulk in the length/width or quality I need, not to mention imports seem to have declined as timber was often ballast on boats coming from Scandinavia. Also with world wide demands on White Pine/Red Pine was needing a lot more planning in my case to order even direct from the forest which was a way I got round buying specific widths/lengths to suit my offcut waste. UK seems not to the best market for Timber exporters to come they seem to get more profits from far eastern market, this may change with economic downturn but has been the case for last 5 years or more. Not to mention felling is done by the calendar and certain times of the year timber can get scarce from Scandinavia we are not alone suffering from holidays.
Last bit of advice if a timber yard do not let you pick your own timber for conformity or twist, pass on a get a supplier that will. I am lucky I have access to timber and can run/mould to my needs. As small Joinery firms have went to the wall or replaced by one man business with no workshop facility. We do not seem to have locally the same supply base as in the 70's for example as all the small Joinery firms had machining facility and supplied over the counter. I spent many an hour as a apprentice making up such orders. But this declined when companies got bigger or thought employing Joiners 714 was better. It is this reason more than any other meant the total decline in Apprenticeship in my area and reduction in employment base for Joiners.