The fact that the brand new master cylinder I bought from Eurocarparts has 4 holes for brakelines as apposed to 2 like the original indicates that it's the wrong one. I was advised just to block off two of them with bleed nipples. This would appear to be, in hindsight, incorrect.
My mate Boab, who has been nipping my head (in a good way) to get the car MOT'd and pulled a replacement OEM mastercylinder from his Aladdins cave of mk2 bits. Not too sure if it'll solve the problem or not but gotta be worth a punt, and I'm a dab hand at bleeding brakes now

Does have a 20 stamped on it so will need to double check it fits, if it's a 20mm one and I have a 16v that needs 22mm, never simple is it?