I've just phoned Toast about a return, and discovered that they still have sale stock available to buy at sale prices, over the phone, it just isn't online.
I was able to get the tapered trousers in a 12 to replace the ones I bought in a 14 because the website showed the 12 as sold out (not sure what I was thinking tbh), and I bought the denim shirt dress in a 14 (need the space up top).
So if you missed out on anything in the sale it is worth giving customer services a call.