Ok Andy, I shall just set the CO pot to a known decent value and get the wideband adjusted (if it can be) to their readings.
You have two faults to fix, possibly related - but maybe not:
1. Establish why the car is idling so rich. (Are you using the stock narrowband lambda still?)
2. Re-calibrate your wideband.
CO pot is for fine tweaking, not massive adjustment so it won't help you much here. I think you have a fundamental setup issue.
Are you still using the standard narrowband lambda? Is it known good and working?
Is the blue temp sender okay?
Which 250cc injectors are you using? Genuine G60 ones, or are they Ford 'motorsport' ones?