Quidco are offering £4.50 back when you buy a lottery ticket online for the first time.
Although the minimum deposit is £5, you can withdraw what you don't spend if you want to from what I remember.
So effectively you get 4 tickets for nothing. Don't forget the money is credited to your Quidco account.
I don't know when the offer ends so be quick just incase.http://www.quidco.com/national-lottery-lotto?edm115