It's quite simple really, you just buy a £1 pay-as-you-go Sim from Orange* for a £1 and then you can use this to grab the tickets.
The process of getting the 2 for 1 is quite simple. Once you get the Orange sim, pop it in your phone instead of your normal Sim, then text Film to 241 or call 241, it'll then send you a message (which costs 35p/text) which you show the box office to get the deal.
How long will the Sim last?
To keep the Sim activated you need make a call at least once every 6 months. Yet this includes free calls to check your balance, just dial 453 from your phone and this will count as a call.
However do remember you have to pay to receive the 2 for 1 text from Orange (it's 35p). The PAYG initially has £1 credit on it and once it runs out you will need to top it up.
When the credit does run out the minimum top up amount is £5. If you know you're going to use that amount of credit for cheap cinema tickets fine, if not just buy a new sim card as and when you need it.
Any possible problems?
Within Orange's terms and conditions it does state 'Text tickets are issued on a priority basis to active customers who spend over £5 per month with Orange. Orange may revise the terms of this promotion from time to time.'
This means it does have a get our clause and while I've not yet heard of anyone falling foul of this. There's always a chance, then again the outlay is only £1.
This was taken from Martin Lewis's MSE. I apologise for not mentioning this previously. I apologise if this has broken the rules and for any upset this has caused to other members...