Ive looked on their catalogue but can't see the actual discs. I can see an overhaul kit. do you have a part number?Only ever purchased brake discs from RockAuto which seem competitively priced and delivered quickly, however, someone else may be able to suggest a reasonable UK based supplier.
EBC look like they have them in stock in UK.
(note they have two listings - above for 70 - 73)
In my early years we used to have them skimmed.
Conceptua Tuning based in Devon have discs
OE Spec Front Brake Discs Rotors x 2 - Datsun S30 240Z L24 Late 1973 Onward | eBay
Datsun S30 240Z L24. Datsun S30 240Z. 1973 - Onward. 2 x Front Brake Discs.www.ebay.co.uk
I’ve bought a few items from them and the parts in question were cheaper than other suppliers
Never buy from them, they just stock rock auto stuff for twice the price or more(even after all the tax/duty.