I sent some money 3 hours ago my BTC client (Bitcoin Core) still says the payment is unconfirmed ?. Any help much appriciated
This could happen for two reasons:
1 - You did not included tx fee in your transactions so the priority of your tx is lower than the ones which paid for transactions network fees. You can check this simply using your TX ID on a block explorer like www.blockchain.info. You will see which is the priority for your transaction and the status of it in real time.
2 - The other reason could be that, as Murch suggested, the network has been over stressed for some reasons and this takes some txs to take more time to get confirmed. However this happens rarely and you should always check the first option before.
-Most likely the recent delay is due to the current stress test, transactions with the recommended default fee (0.0001) currently can take hours to confirm.. if you sent the transaction with less than 0.0001 then it will take allot of time particularly with this "stress test" (and if the value of the transaction is less than 0.01 then possibly days).