I don't know how currency works in the UK but I can still solve it.
255 total coins
1/3 are £1 coins
255/3 = 85110 of the coins are 50pp
110*50pp
so we have 5,500pp whatever this means
£85
255 - 85 = 170
we have 170 coins left
170 - 110 = 60
the last 60 coins are 20pp coins
60*20pp = 1,200pp
1,200pp + 5,500pp = 6,700pp
£85 + 6,700pp
whatever this means
edit:
85x £1 coins
110x 50pp coins
60x 20pp coins