Normally I'd not go near B&Q for timber or sheet goods but a couple of weeks ago I had a non critical need for some 12mm ply that was not structural or going to be visible and I only needed a small piece so I donned deep disguise and slunk into the local branch.
I was quite surprised to find this was pretty good
nominal 12mm measured up at about 11.4mm outer veneers were about 10 thou (0.25mm) so very very little scope for sanding but the upside of the thin veneer is that it hardly splinters when cutting with a decent blade on the tablesaw as the is possible nearly as much glue as veneer!
On a number of cuts I only found one set of voids
The make up is 7 plies plus the veneers
Not quite a fine as 12mm real Baltic Birch (which usually also measures up slightly undersize)
My sample has 9 almost equal plies plus you can just see the outer facing of phenolic resin which would not normally be there on standard Baltic Birch ply
Unusually virtually the next job into the shop needed a lot of very lightweight ply so based on the 12mm experience I looked back in B&Q at their 5mm offering in the same range.
Marked as 5mm but beware it was barely 4.2 mm. Fortunately I had not machined the grooves that is had to fit into so I could accommodate the thinner stuff.
The lay up is three layers plus the perilously 10 thou thin veneers
I had a whole 8x4 sheet and cut this into 10 components for the job so many metres of internals exposed and not a single void spotted
I don't know if this is a move by B&Q to up their reputation or I just got lucky. Looking in detail at the labels you can see this stuff is destined for several of their outlets in UK and the EU that are all part of the Kingfisher group. Maybe they have decided that a better quality product will give them less grief? who knows.
Caveat Emptor
Bob