I have now spoken with Pipewerx, and they are willing to fabricate an adapter for me, based on the quality of their systems I think it will be top quality and it should come in at less than 20 quid. The only issue is how long it will take them as the car is booked in next Wednesday for service and MOT and my mechanic has allocated time to fit the downpipe.
Edit: Adapter now ordered from Pipewerx, 16 quid posted which includes 2 x band clamps. They said they would make it today and get it in the post tomorrow! Happy days.