Please find the photograph of the completed installation. The belt is loose as I have now winterised my engine and did not have a camera when I had the belt tight. Works a treat with good alignment. I found a 410J x 10 rib belt the size to use. The alternator is a Leece-Neville 90A, Model number 8MR2069TA, shaft diameter 17mm. I look forward to the start of a trouble free season next April!
Many thanks for your help and advice. Regards PR