ESP light on

Yes, I'm pretty sure the ESP light on all the time is now an MOT failure.  If you can confirm the fault is the dreaded C0131 code, then , if BBA reman have a repaired replacement in stock they will send you that one...  you remove the faulty one and fit the new.  Then just return the faulty one to BBA reman.  This way, your car won't be off the road at all.

If however they don't have the correct unit in stock (as in my case), I sent it away on a Monday and received it back, repaired on the following Thursday. So ... not too long.  If you need a vehicle for those days it will pay to hire one for a few days.  Its still way, way cheaper than fitting a new unit at Vauxhall (which would probably fail again in the future!).  The BBA reman repaired unit is guaranteed for the life of the car.