Usually the spread and broker fees make the profit a lot less. I would be amazed if you could make any kind of profit with that level of investment in a Cambio!
There are plenty of online forex dealers you can use, but tbh, what is a better deal is to spread bet on USD.
Your thinking is USD will get stronger vs GBP again. Thats fair enough, but if you know the timescale also you can place a spread bet on the exchange rate and get your return tax free.
Is it a wise investment though...well i would say unless you are happy with your economics it's a bit risky. The dollar is weaker and the US defecit large, which means that US goods wil be much cheaper in the US than foriegn. If you know your consumer trends it might be worth a punt on some US Consumer Brands or maybe Manufacturers which will be selling cheaper than the imports...unless inflation bites them of course!
This should in no way be taken as investment advice!
Safe Investment for 2k - a good rate Cash ISA!!!!