Well. Don't rush. There are LOADS of these training centres. You have to shop and ask around for the best prices and reputations.
At your age (No offence) I doubt your wanting to spend 3yrs at college so I presume this is why your thinking of going down this route?
I have just returned to the UK and was looking at doing one of these courses but, to be honest, the prices put me off. You will be getting quoted anything between 4-6 grand. It's a lot of money to lay out and then you have your tools on top of that plus no guarantees of work at the end of it (I'm not trying to put you off. Just stating the facts as I, personally, see it).
I suppose it all comes down to how much you want this and why you want to be an electrician.
Don't think your age will work against you. Personally I think if anything, it'll help. Life experience, emotional maturity etc.
Are you wanting to become a "Full" electrician (which basically means all types of work. Commercial/Industrial/Domestic), in which case you will need the C&G2330 or would you prefer domestic work only? If the latter then you should look into the EAL Domestic Installer course.
I hope this has gone some way towards helping you?
Any more questions then please ask away. Plenty of guys on here will give sound advice.