Had a new stainless steel  flexy pipe fitted to exhaust, as the original had sheared . I was quoted £400  for new catalytic convertor at kwik fit but found a custom exhaust builder who cut out and replaced flexy pipe for £140 . An engine mangt light has come on, could this be due to work done and it just needs reset or should i expect another issue . The car is running well and doesnt seem to have any issues, what do you guys think .

 

Think the first thing to do is to get the codes read. It seems like a coincidence that the management light comes up soon after you've had some exhaust work done. The lambda sensor(s) could have been upset when they presumably removed the exhaust to fit the flexi.

for £140, you could have got a decat pipe from the turbo