They make their money on the rate Clive. Sell for £10, buy for £8 that sort of thing.
Ah, well in that example, surely the £2 is their commission, no? Unless I've misunderstood something.
Usually they take the exchange rate then add 1.5% as their profit/commission/fee, but the 1.5% will vary from bank to bank to exchange house to hotel reception... depending on which one you choose.
Even the exchange houses rates here vary a lot.