OK, I’ve done a bit of Googling and can now answer my own question. With the previous two VAT increases (15 to 17.5% and 17.5 to 20%), the change was announced in the budget and took effect from January the following year. Although we aren’t in normal times at present, so anything could happen, my sense is that any increase won’t happen overnight and will take effect from January. On that basis (with my daughters new car due in 3 or 4 weeks time) I’m hoping that we may dodge a bullet!