Thank you
All,
thank you for your very helpful replies, much appreciated. I already had most of the "pieces of the jigsaw", so to speak, but I am now able to put them together in a much more coherent fashion.
One thing I had been taught (erroneously) was that conventional flying controls became ineffective at high transonic speeds, which clearly is the case for some aircraft but is not always the case. It seems to me that the issue is essentially one of control authority, i.e: are the control surfaces big enough; can they deflect sufficiently; does the authority remain sufficient to cope with the main wing centre of pressure movement; and is the airflow over the horizontal stabiliser and ailerons (or elevons in the case of a delta) sufficiently clean and attached to allow control authority to be retained. Truly a complex topic!
Thanks again.