how best to sell excess holiday cash: Swiss franc CHF back to GBP

popalock

I have a quite of Swiss francs in cash, about £1000 worth.  Clearly there aren't that many people who exchange it because the bureau d'exchanges I've contacted have a massive mid-bid spread, like 10%.  So this means on £1000 worth of CHF I'm only going to get back £900, which is clearly better than nothing, but not very fair especially when you consider that GBP to EUR can be as low as 0.5% against the mid rate.  Does anyone have an idea how I can best do the exchange?  As it stands it's almost the same price to fly to Switzerland, do the exchange there (to GBP or EUR) then fly back again, rather than just do it here..