I'll have �600 this month, what small-caps stocks can I invest into that possibly have the greatest potential?

I am currently 18 years of age and looking to invest into some small market capitalisation stocks, (not penny shares - thats gambling!), but stocks that are of relatively new companies that are just starting to rapidly grow if you have any information? Also, I'm a UK based investor and looking to find a cheap online stock broker I can use? Please all help would be much appreciated. Thanks.