Guys, I'll give you the low down.
1. The seats are only in the exit rows that recline. The seats that don't recline are'nt classed as "better".
2. If someone moves during flight , it just will happen. The payment is for a seat that is confirmed to be in an exit row. If your willing to rock up and hope for the best, go for but if you don't get an exit row don't complain.
3. Whoever sits at the exits have to be cleared at checkin. The ticket is booked through the call centre and can't be booked over the net. If you don't tell the truth over the phone about your able bodiness. You will not be sitting in the exit.
4. If the flight is cancelled and on the next flight you are unable to sit at the exit row, you will get a credit shell that lasts for a year.
Hope that clears it up a bit