The coal tar soap available now is indeed fake due to EU restrictions on cosmetics, unless under prescription. The 'fake' stuff has actually got tea tree oil in it to provide the anti-bac instead of coal tar.
My next door neighbour (General Store) sells the rough 1lb/2lb block Carbolic soap and claims the common Falcon 125g bars aren't really legit. He can get the Falcon cheap too, 40-50p/125g bar.
I could bring some of the 'proper' stuff to the Moot if people want it. I'm guessing an impressive 2lb (900g) block would be £3.50-£4, same price that you'd normally pay for the 1lb block.