just asked the same question on jonathan s build tread not in the uk but i am about to order a couple of vents myself from the states my parents will be at their house in the next couple of so could get four and then post to you if you like them link to the vent is
Guys .......Ordered 2 THV 45`s on thursday but they sent TRV`s same valve but without the 90 outlet.They are intended to go direct into the tank but they should work ok remote mounted.
Cheers Stew ( nice red anodised alloy valve by the way )