Generally I pay by credit card OP. Just hand it over and let her do the necessaries whilst I take a shower. Sometimes, if I trust them, I just hand her my wallet and say 'Take your pick'. Gift tokens are another method I've used as well as Green Shield stamps. One girl accepted nectar points as well. Plenty take gift cards which are widely available. Shop vouchers also make their eyes light up. Unused foreign currency can also be a good way of doing things or a big jar of coppers.
FFS OP are you for real - its cash, cash or fucking cash. Will your pocket money run to an escort though?