Hi Bill and thanks for your warm welcome and indeed for your swift reply.
I have bit the bullit and so far have got the main case off ( thanks ) ... but not yet the front facia panel which looks quite complex.. ( I am no engineer !! )
I will wait for daylight and then try to get further ... I can now see the rogue pot , and replacement should not be too hard once the front is off ... thanks again ... I will let you know how I get on !!
Derek