Camo Trousers

During WW2, the British did not have 'camo trousers' - therefore nothing can pass for authentic wartime camo trousers.
The only thing close to 'camo' trousers issued, was the lower half of the two-piece set of camouflaged windproof over-suit issued later on in the war to infantry.

They're Belgian trousers, as used '50s-'70s, in a camo print used on the Belgian copy of the Denison smock (the camo of which is not a copy of any one of the various Denison camo prints used during war-time or post-war). You used to be able to see ignorant WW2 Brit' para' reenactors running around in matching Belgian Denison and trousers thinking they were the dogs danglies, when really they were massive embarrassments to history and the hobby. Belgian Denisons are passable for airsofting as Brit Denisions if you've got one or get one for peanuts, but best save money for a better cheap or decent repro'. The trousers are only really ideal if you're reenacting the Belgian Congo wars.

(Also, those pair are way over-priced - I bought an unissued set recently as general out-door trousers [hey're warm and waterproof without being too heavy!] for a tenner)

As above, those are not correct for anything I've seen.

Closest things you can get to 'authentic' British WWII camouflage trousers are the windproofs issued to the Lowland Division and a tiny handful of special units. There's a pic in the kit guides I think). Otherwise it's the SOE jumpsuit for you old chap, ideal for looking like a right plonker!