Question Author
Thank you AC for all your effort and helpful advice. But let me confess the truth.
When I had the memory upgraded, the lad who did it plugged the sound cable back into the socket marked speaker. Have now found out it should have been in the socket with a pic of soundwaves!
I should have checked, or even thought of it as a possibility, but DOH, I didn't.
All's well that ends well, but I feel a "bit of a nana"
Thanks for your input. Guess with my lack of technical knowledge I shall be back for further advice at some point in the future.