Right, progress update...
I've followed advice and bled the brake and installed a new TPA and unfortunately neither of which have worked.
The right hand side slave piston is unstuck but seems very slow and lazy and the brake lever is unresponsive, spongy and almost light feeling when you pull on it. There is no definitive "thud" feeling like I used to get when the right hand pad hits the rim and it just generally feels like nothing is happening when I pull on the lever.
Could it be an air leak or something or would fluid pour out if this were the case? I'm pretty sure that the slave piston is a factor (but I'm sure it was always slow) but it still doesn't explain the feeling of something not right when you pull the lever....or does it?
Any ideas guys before I box it up and send it off the experts?
Thanks in advance
Chris