Sytner Coventry got back to me, they have changed there mind. They need to do some investigating work first at
£85 + VAT and hour

then the cost of any additional parts and labour on top of that.
Wollaston Mini in Northampton have quoted me £32.50 to diagnose the problem then any parts and labour on top.
Have booked in at Wollaston Mini Northampton a week Saturday to have the problem looked at. Fingers crossed the tensioner just needs to be adjusted.
There is a local garage that does free battery checks, going there on saturday first.