Apple will surely swallow a lot of the increase, if not all of it (at least on the products already being sold at an exorbitant premium, which is most of them).
The psychological difference between £499 and £510 for a good can be vast.
Apple cut their prices when the VAT dropped to 15% and increased them when it went back up to 17.5%.
Apple will pass on the increase when it goes up to 20%.