Having run three LPG cars in the past, when diesels were stil slow (2000-2004), I have to say I really loved them. Have never really been tempted to convert my MINI though as you lose too much of the storage space. In my previous cars all I lost was the spare wheel well.
Sounds like you got a good price for the conversion. last one I paid for was £2250 minus £1100 government grant which was the going rate pretty much at the time. Was by far the best conversion I had. LPG is good but don't think i'd bother again as diesel technology has come so far recently, unless of course I buy a thirsty classic car.
Anyway too my point the engine management light. I had a gas converted Focus that would run fine with no lights first thing in the morning but if you turned her off briefly and then started your journey again the management light would come on. Would reset over night. Apparently the engine was sensing low emissions and assuming things were going wrong so put the light on. What it needed was an inhibitor on the light ,or on an O2 sensor, to stop the car thinking there was a problem. Company I worked for never put that right so spent two years with that damn light on.
Happy motoring.