BEXIL160 I think some crankshaft mods were put in place which seemed to resolve the sudden stoppages!
ARV's are a delight to fly, lovely handling, light but not twitchy comfortable except for the lack of a heater and they have a stick not a yoke. Add in the excellent visibility due to the shoulder wing layout and it's like a mini warbird.
The original 75hp engine isn't really enough for a good climb rate. Two up with a full tank and it can be a struggle on a warm day. From memory, the Rotax conversion involves putting a 12lb lead weight in the tail to counteract the C of G shift caused by fitting a longer, heavier engine. This reduces the already not too generous load carrying ability.
Mid-West have also fitted their 100hp Wankel rotary engine to an ARV which transformed it apparently. There was a Pilot or Flyer article about it a while(??) ago.
The only significant weakness I can remember the flying club complaining about was the step up into the cockpit which was a tad flimsy for club use. Checking to make sure that BOTH latches on the cockpit lid were closed was a must. Taxiing with a central brake handle took a bit of getting used to but the brakes are quite effective. Not having a heater on an aircraft with a liquid cooled engine was barmy, especially in a UK winter.
All in all, a lovely little aeroplane especially if you can get a Permit one. I've only ever flown the Hewland engined version but would imagine that a Rotax powered ARV would have a bit more get up and go.
Check G-INFO on the CAA (caa.co.uk) website, that shows the owners addresses and risk peeing them off by contacting them! I don't think any flying clubs use them now but it could be worth browsing one of the where to fly guides.