I made the bracket as reported, I reduced the idle speed down to 950rpm & I took the car round the block. I can report dear reader, that the burbling idle problem & the hesitancy on acceleration have just about gone! I took the Fury to work the following day & even through the Farnborough traffic it behaved itself.
So an HUGE thank you to Andy at OMEX. The problem never was with the OMEX ECU, but it was his analysis of the datalogs that identified the problem with the throttle cables. I have now set the ECU to run "closed loop" (the lambda sensor in the exhaust is sending signals & the ECU is adjusting the fuelling based on that) & little by little the car is getting more - car like. There are less & less things that need my attention.
The starter's still making a dreadful racket though.