Security/burglar alarm under £90

dellboy102

hey
I was just looking for a burglar alarm, about 1 PIR, wireless, and it has to have a external siren. (the siren box goes outside the house)
the thing is we saw some from argos such as yale for £99 which we wouldnt of minded purchasing however the thing is it only has one keyfob, a family member in the house works a night shift hence when he leaves the house he needs to activate the alarm, however someone in the house might go to the loo and active the alarm so we need a way to de-activate it but since it only comes with one keyfob theres no way to do that.
the cheapest we can find which has a keyfob AND a pin number entry system is £150, this is way beyond our budget, in fact we wouldnt mind if only a pin keypad was supplied and no keyfob.

Any help much appreciated