I believe the personal tax allowance for someone born before April 6th 1938 (which I was) is £10,660 and not £10,500 as stated by you. This will obviously make a difference to the calculation.
Thank you very much for your help. Have phoned the tax office who have agreed with your code but are not able to give an explanation of
their previous tax codes! They will hopefully implement 736.
Again thank you.