Apart from the fact that I got clipped round the ear early on for implying that my wife kept on moaning, the outcome of all your contributions was that I then got a pat on the head as her next effort was successful, almost I think for the first time.
What did it ? A crushed Vit C tablet and, following the advise from Peter on his experience with the Morphy Richards, the yeast was put in with the water instead of being added at the end - the instruction book was adamant that its sequence should be followed !!
Many thanks for all your contribution, guys - the query produced far more responses than I did ever expect and I hope others got something out of it too. A particular thanks to the Vit C recommenders and to Peter for his experience.
Rob