Good question, with the way the central banks are dropping interest rates it is certainly not worth leaving in a bank, even some of the better performing deposit accounts aren't much above inflation at the moment, and Interest rates only appear to be heading south in the short term. The current policy of dropping interest rates to stimulate the economy appears to be encouraging people to get further in debt and punishing any one with savings (and easy credit was a large factor in getting ua all into this mess in the first place).
Anyway back to your question, two years would seem to be too short a term to ensure a return if you invest in the stock market and probably entails too much risk as you need the money for your wedding. Sterling is expected to return to more normal levels towards the end of the year, but a play on sterling would be speculative and there are no guarantees.
If you are looking for a safer option you might try government guaranteed corporate bonds, see: [broken link removed]. It depends on how risk averse you are. The turkish interest rate is currently running at around 17% so I know a few people who have opened deposit account over there and made good returns from these. I dont think the Turkish govt guarantees foreign deposits though so there is some risk if the bank goes under. see [broken link removed]
Probably the best advice is to see an independent financial advisor or your bank and see what advice they can give you.