Is there a way of resetting the Engine Check Light...?

I would have thought that disconnect the -ve terminal from the battery for about 10mins…but does not seem to be working.

I am running a PowerFC.

 

If it is on then you still have a fault somewhere.
Without checking how you have wired in the AVC-R and how RC Developments fitted your Power FC and boost control kit it is difficult to diagnose from here.
The pics you sent don't really help, there are too many sensors without plugs on them, all the OE sensors in the engine bay should be plugged in to the original loom, the only one that can be unplugged is the original boost solenoid.

 

Resetting the ECU is a job i have never had to do myself. However iirc from previous threads disconnecting the battery for at least half an hour should do the trick. Disconnecting for just 10 minutes may well not be enough. See how you get on with that.

 

Ooops, didn't read the question properly.