Thanks everyone for your input.
I must admit I agree with Guest 55 for all the reasons she gave, at least the ones I understood
(gave up Maths after AS). I certainly can't agree that the grid method is slower, and even if it is for some people, isn't it better to spend 2 minutes on a problem and get it right than 1 minute and get it wrong?
Took dd to have a chat with her teacher after school yesterday. She helpfully pointed out a few occasions where had made silly mistakes using the long multiplication method and asked dd to identify where she had gone wrong, which she couldn't, although I suspect it was her old enemy, place value!
Think she might finally have come round to my way of thinking at last. Now if I can only persuade her to read the questions properly.........