Update no.2
It's fixed. I collected the car from Stratstone on Monday evening - they told me that they had tightened all bolts at the rear of the car including the rear sub-frame which cured the problem. Unfortunately on the way home I noticed the air conditioning no longer works - a job for the next service before the warranty runs out.
Remember the A/C doesn't work if the heater fan is turned to "off"... The A/C light flashes and nothig happens.
Wiscos beat me to the post!
