Difficult to appreciate that the relatively small amount of leakage on the valve (a few drops at tickover) was sufficient to cause the management system to shut down at higher revs/load conditions.
Brilliant to have the vehicle working correctly however, thanks Richard.
One teensey comment however; running no more than 1/4 throttle and treating the accelerator like it's made of glass to avoid the thing cutting out is a pain in the proverbial but it gives you quite amazing fuel consumption!!