Jim K writes:

at least in Wickes, say, I could select the wood myself and reject
anything that's twisted.

IME finding straight and defect free lengths in Wickes or any shed is
a waste of time - all of it is ****e usually strapped together in
packs that appear straightish, until you cut the straps and boing! it
all goes banana shaped and reveals all the dead knots, sticky resinous
knots, splits, shakes etc etc = utter crap..

Certainly true in the past. But in one branch of Wickes recently, I was
surprised to notice that none of the CLS (at least) was strapped into
bundles with separate single/ pack prices---all was loose with one
price. Could be a change in policy?

get ye down to the woodyard/timber merchant/sawmill and pick your
lengths there - your chances of getting stuff that you want will be
infinitely increased.

Also if you are buying a reasonably large quantity (discount) or want
something slightly out of the ordinary (which is all the sheds have).
Might be a bit OTT for Bert's project, though.

--
Mark