that is going to depend on what the stock market does. Have you thought about an investment fund ISA? You get experts investing your money and can spread even quite a small amount.
I keep recommending this book and will do it again
Amazon.co.uk User Recommendation
you might also like to go and look at the M and G website, not with a view to investing, but because the explanations are clear. I have investments with them that have done ok but I don't suggest the website for that reason