How much is it for a IPhone?

I want either a IPhone 4s or if possible IPhone 5:) I have saved up £240 from nearly a year of saving up from my pocket money (I'm 14).

It depends. I have a iphone 5 and it was $700

Looks like you are in UK. Do they have it on contract there like the US has?

The straight talk apple iPhone 5S 4G LTE 16 gigabytes, is about $650.00. That's what I paid for mine.
I'm 16, and I work so I had to save my money for one, but since you're still 14:\
I don't know about iPhone 4's, but they are probably much cheaper now, or even cheaper for a used one. You might have enough for that.

In your budget, you'll be able to get iPhone 5 unlocked. Since you're below 18, you can't sign up for a contract but can always go prepaid. If you need iPhone 5 SIM-free cheaper than retail, mail me.