In Argentina, the easiest way is to go to a Western Union office and deposit cash for the transfer plus a commission which varies with the amount of the transfer. For $ 100.00 they charge 16.00, for 1000.00 aprox. 30.00, and so on. Pretty expensive, but the transfer is immediate via Internet. They give you a Transfer Number, then you send an e-mail to your correspondent giving him that number. He can collect immediately in any local Western Union office. Cash to cash in less than 5 minutes.
I guess in UK the procedure is the same, but surely less expensive.
Un abrazo - Andrés