Thanks everyone for your answers, I am still in two minds about what to do I must admit, saving myself money on the one hand weighed against making a mess up of things on the other.
KDowson I take your point of installing in-line ball valves to switch the water pipes off at various points while working on others. I had been thinking that I need to do this myself, I am just not sure if I 'dare' take the job on, but as you also said I'm sure it would be rewarding to look back on your own work if possible and of course much cheaper too.
iron28 yes I agree we are on the Oystertec thread and I would love to be able to go into my local diy store and see the connectors, I wonder what the delay in getting them into the shops is? I have bought (and sold) some Oystertec shares myself a while ago so I was interested in trying to put the product into use.
Anyway we have only just decided that we should do the bathroom up and we don't have to do it immediately so I expect I shall go through a bit of torment before I decide whether to 'splash the cash' or attempt it myself.
I thank you all for your helpful replies. Cheers