Ask a few questions!
I would very strongly recomend that you take a good look around the market and ask a few questions like:-
Are landings included in the price?
Is more than 5 min of pre/post flight briefing included in the price?
Is a fuel surcharge included in the price?
What happens if your account goes in to the red, do you loose the discount on flights already made?
Is VAT included in the price?
Ask the question of Cabair, Airways flying club (at Booker), WLAC at White Waltham, Billins air Services at Cranfield and SFC at Stapleford.
And then can I have 10% of what I have saved you for the advice.... Please?