This is the master cylinder internals, the shaft has a plastic coating that has started to peel , there was bits of plastic trapped on the seals and were badly scored, the oil was also very dark
Hugo, I wouldn't waste time with the official dealers as they are tied under contract to buy spares in from MMC & then re-sell to end users
Jump the queue and save a few ££ and try Cain at Wolf Performance, great knowledge and generally has stock of common stuff that fails (like brake & clutch hydraulics) https://www.wolfperformance.co.uk/