He's not tight, he's a financial vampire.
You know you'd be better off without him don't you?
£70 is nothing. You'd save far more (council tax, food etc) if he wasn't living with you.
I'll bet he eats £70 in food - he's living rent and utility bill free whilst watching you struggle.
He's not got any redeeming qualities. He's a selfish prick whose using you.
Kick him out and as other posters have said he can see exactly what life £70 a week buys him (thought doubtless he'll find the money when pressed to find his own lifestyle).
Oh and he's not saving for a mortgage btw. After 6 years you're not married, he is still sponging of you and expecting petrol money.
The good news is that it seems you're in control of the rent and it's your home.
Find some bin bags, throw his stuff in them and kick them and him in the gutter where he belongs.