Creating a change table - £0.01-£0.50?

[Pedroski55]

Well, I thought the Brits had done away with 1p, but the Internet says:

The following coins are legal tender in the UK: All regular circulation coins: 1p, 2p, 5p, 10p, 20p, 50p, £1 and £2 pieces;

Looks like a job for modulo! Find the biggest coin that dispenses the maximum amount of change, then work on the rest.

Someone sticks in a £5 note, but only spends £3.01, how to allocate the change?

And if some coins are already gone?