First,thanks for the replies. Appreciated.
Mybike is 5 speed.
Riding back from town yesterday it felt as the slippage was due to the chain not engaging with the sprocket,if this makes sense. It just slips,somehow. Its not as if this is a big thing,but going uphill with a car or a lorry behind,and with a dicky back and arthritis,it makes me uncomfortable(once over 65 you sort of realize you'e not immortal!). Also(the slippage),isn't happening all the time. All said,I just like my ride 'just so',so that I don't have to think about 'is my back about to go,foot slip,as I go up this incline'.
I don't have it in me to go out to the garage to go thru things at this time of year. As the matter seems(at present)undefineable,I wonder if any bike shop can resolve it,given that it would take a ride out and some hills,to test it under load. 'Yes,fixed it' says the mechanic in the shop. I take it out,it slips,no,its still there,says me. I know this stuff can happen.
Further comments welcome. Ta for advice