It will make no difference to either the dealer or Motability with the fact that you only placed the order for the Q2 2 weeks ago, the order will still be at the 1st stage ie, sat doing nothing, no build slot or anything so cancelling it to change to a car you can actually test drive is a no brainer and I’m sure Mota wouldn’t be happy that Audi had let you put an order in without giving you a test drive either.
Give Motability a ring and tell them you want to cancel the Audi as you’re not happy with no test drive and because you have a test drive of the BMW on monday and will probably be ordering after that, you need to cancel 1st tho otherwise you won’t be able to put the order in with BMW.