No hidden cir clip, but have realised that boot fits over main body and is really tight. Just one more thing the piston, I am assuming the pointy end goes toward the main body and the flat end comes out of the end of the boot to the arm. Sorry to appear so vacant but people have laughed at me when I said I was going to change my own slave cylinder (mainly because I am female) but I have read lots on here and found a guy who has done a photo blog when changing his on a 145, I will just ignore the bit about battery but slave is the same.
I have all the correct spanners and bought myself an eesibleed today. I was bought up that if you put your mind to something you can do anything. So I will manage it although the air may be blue in Devon tomorrow! I can upload a picture of parts if necessary. Thank you for your help