You could look at a 4 channel video DVR PCI card, which would cost about £9.00 new on eBay.
Serif was offering a £12.95 'promo' special security camera program, with motion detection and contact possibility a short ago. Cannot find the details of their email, but it might be worth a further check.
There is a forum member who deals in security cameras and accessories. Perhaps if sees this posting, he may provide links etc?.
Sorry that I cannot help any further.