ok, thanks a lot to all so far....
trench dug and 28mm yellow MDPE in to take 21m run from house to garage to run combi.
i have done plenty of plumbing (including gas inside house) with the help of the group and intend to make the gas connections and get it all checked by a corgi at the end.
I intend to terminate the connections as transco would, buying all the stuff off BES website.
will this be ok with no special tools - MDPE to outside wall of buildings, GRP risers and cast iron through walls?
thanks again paul