Thanks for all the advice guys I have cracked off the brake pipe for the rear right at the master cylinder and there is no pressure from the rear output even when the motor for the abs pump has been running for 2 minutes. (the workshop manual says not to let it run for more than 2 minutes) It threw me as I tried the original and a second hand master cylinder and had the same problem with both but then again the second hand master cylinder had been stood for a long time too so I think I might just have to buy a third one that I know has been working on a car relatively recently.