Hi Lou, I noticed you hadn't received a reply - I haven't done this but I know people who have so I thought I'd pass on what I know.
You can either send the money via the Western Union website, or phone, or go to an agent. You pay money to them, they 'transfer' it to the receiver and issue you with a 10 digit number which acts as a confirmation. You give this number to the person who you are sending the money to.
The person the other end goes to their agent (ie Western Union in Candolim) and give the 10 digit number. Once they have confirmed the details the money is theirs. You need to ensure that the name on the receivers identification matches the name that you give.
It works out at around an extra £12-14 per £100 that you send and if you pay from a credit card you may get charged extra by the issuer as they may class it as a cash advance. I'm sure you can pay cash at an agent but you need to take a form (or 2) of ID. There are loads of Western Union agents worldwide and you should be able to find one close to you if you don't want to do it online.
Have a look on the Western Union uk website and you should get more info there.
We've never done this but we always make sure we know where the nearest Western Union agent is abroad in case we need to call on the Bank of Parents!
Hope that helps, let me know how it goes x