Thanks. I've Just finished doing this. For anyone else reading this who has just changed their slave or master cylinder and the clutch pedal has 0 resistance this is what I did:
I went to halfords and got the Gunson Eezibleed kit and a litre of brake fluid. Set up the gunson to a spare tyre and screwed open the bleed nipple quite a lot until I saw the fluid coming out.
Keep it going until no more bubbles come out and the fluid runs clear then tighten up the bleed nipple.
Go check the clutch pedal and it should be firm.
Keep repeating until you think it's all clear of air.
I had previously tried using a vacuum bleeder attached to an air compressor to suck out the fluid but after using the gunson, it looks like it prefers a pressure bleed instead.