Cheapest and most expensive cinema tickets in the UK

emujuice

ok, please forgive my dishonesty if it offends you!
I just moved into a new flat and got a cineworld letter through the door, thinking it might be some discount vouchers, i opened it even though it wasn't addressed to me.
It turned out to be the previous tennants cineworld unlimited card. She moved out about 3 months ago...the thing is, she looks quite a lot like me...
I haven't used it yet and probably won't. But i was just wondering how the proceess of using them works...If she realises she's not got her new card and cancels this one, will it just not work? I don't wnat to use it, in case she tries to cancel it and can't as there's a record of it being used. but i figure if i try in a couple of months she might have cancelled it but it might still work.
Am i going beyong money saving and being dishonest?
And sorry for opening mail not addressed to me. i did it by accident on some other stuff (well my OH did) and found the person has lots of unpaid debts coming to the address, so we're opening some stuff that looks like it's debts so we can inform the companies involved that they don't live here, before the bailifs come round!

emujuice

bump - wonder if anyone knows the answer to my unlimited question? Cheers