BES Plumbing (good mail order plumbing supplier) has a 12L expansion vessel and filling kit currently on sale at £42.
here's a pic of the full kit (part 20244), which includes 3 bar pressure relief, guage, double check valves etc. whilst it's not strictly solar rated, it'll be fine provided you plumb at the end of a pipe laid in such a way as the pipe dips below the solar loop and then rises up to the EV, to minimise the heat reaching the expansion vessel from the solar loop. plumbing the EV in the manner pictured in the attached (i.e., air valve on the bottom, plumbing connections on top) will also help keep heat away from the rubber membrane.
Hi guys,if id known you where gonna put my drawing on here id have done it neater,looks like my wee lad done it lol. Just doing my shopping list now as to what i need (been busy) to price on monday. We have a contractor in work who says im welcome to price stuff in his name so hopefully get it a bit cheaper but ill be comparing prices before i part with my hard earned cash. No questions yet but they,ll be coming shortly.
Your diagram is just fine, you shoud see some of my diagrams and then you would thinks your's is really neat).
Both Stewart and Austen are pretty much at the stage of putting togather an order of their bits and pieces. I had suggested using BES for much of it but I know Austen has another catalogue suppliers whose price look good.
Stew,Austen & myself were planning on meeting up (probably at Stew's , Lisburn) in the next week to run through what the two of them need if you want to join us?