I've just set up an account with Invest Engine, following a Money Saving Expert article on their website.
Here is my referral link: investengine.com/referral-welcome/?utm_medium=share&utm_source=growsurf&grsf=j8dk04
Just to be clear, I will get a £20 referral bonus if you sign up and you will get £20 too for your account. You need a minimum of £100 to create a portfolio.