Its a flexi hot pipe from B&Q,..
OK, I went there today looking for a quick fix to get it set up over the weekend, but decided to save loads by ordering bits online!
For the water in, I was going to get a hozelock tap adapter and connector, but now I am wondering whether this would work instead: Its a Shurflo 1/2 barbed wingnut straight fitting £2.22 (normally on out side of shurflo pump)

And for the gas, the US regulator that came with the L5 has the correct fitting at the heater end of the hose, so did you just cut the black hose off and jubilee clip it onto the UK regulator?
Thanks