A British 1949 cupro-nickel Florin (Two Shillings)(George VI), uncirculated and in absolute mint condition could fetch up to £20 GBP. If it has been circulated but still in good condition, it might fetch up to £5 GBP.
The values quoted are the best possible for the best specimens in their grades, but may be significantly lower due to varying demand for the coin and the prevailing economic climate. A reputable coin dealer will be able to give a more accurate valuation based on inspection of the coin.