Seeing as this is basically travelling from A to B to C on public roads isn't it covered by your standard SDPC cover? I don't see how that can be classified under "Motorsport" or "Rally" day.
Seems a bit extreme as to why they are voiding your policy for asking and I would (However wrong it may be) cancel the direct debit. Definitely wouldn't pay for something I'm not getting and would cause a major inconvenience.
There are a few Insurers/Ex Insurers on the forum, lets hope one of them sees this!