I think all is not well with my R90E - the engine cut out as I turned into the end of the farm track this evening, and wouldn't restart on gas. Eventually it restarted on petrol, after a bit of farting and coughing.
Driving the gas solenoid on "by hand" resulted in a loud hiss that emptied the line almost immediately (only hissed for about a second). I'm pretty sure it shouldn't do that. I opened up the vapouriser but couldn't find any signs of split diaphragms or anything, but I strongly suspect the vapouriser has had it. It was leaking quite a bit of coolant, too.
I had a quick look on Tinley Tech's website but they seem to be out of stock of R90Es. They've got some others ranging from about 50 quid to a couple of hundred quid - is there much difference in performance in a closed-loop system? My local LPG fitter probably has multipoint vapourisers, which I guess are no good for my singlepoint install.