Great item if you wish to restrict access to only your cats providing they have been microchipped. I haven't installed / received yet but looks like just the job. Most other places £95+.
Full details: http://www.sureflap.co.uk/
TCB: £3.24 shown as pending
Voucher Code: mvpdecember (-£5, ends 19th Dec) or try petsupermarket110 (-10%)