You might find some Philmac universal-transition-couplings handy for joining lead to blue plastic MDPE pipe. http://www.philmac.co.uk/products/universal-transition-couplings/ One thing with old lead pipe, you start poking/ moving it, I guarentee you, it will spring a leak elsewhere. Had lead pipe in outside toilet leaking,repair it, following day it leaked under shed foor, then garden, ended replacing about 7 mtrs of lead pipe.