I recently handed my CV in at millets and the way the bloke spoke to me seemed very positive and noted down a few things, so positively thinking, if i get the job how much should i expect?
I assume that meant to read '15 year old'. If so, the National Minimum Wage doesn't apply to you. (It only applies after school-leaving age). So an employer is free to pay as much or (more likely!) as little as they like.
However many employers would pay the National Minimum Wage which applies to 16 & 17 year old, which is £3.68 per hour
The rate for 16-17 year olds is £3.30 an hour. 15 year olds have no minimum wage entitlement as they are below the statutory working age, which is not to say they can't work, it's just they have no right to the protection offered by the minimum wage.