Thanks guys, for your prompt response, namely - 'Jeebowhite', Dan62 and 'flying Clutchman'. It's great to know I can always get help here.
I've taken your combined advice on board and will be ordering a replacement master cylinder and then it will be down to the nitty gritty. If any one can offer any tips and advice on how best to tackle this job, I would again be very grateful. (My Haynes manual leaves a lot to be desired).
Once again, many thanks for all your help. I will post the results as soon as I've done it. (weather permitting)