The CANP system is used to notify military aircrew of the area you are planning to take off from. Additionally, it links through to NATS (National Air Traffic Services) and activates a NOTAM. CANP submissions are processed by an organisation within the RAF called the Low Flying Booking Cell (LFBC) which operates during normal working hours, Monday to Friday. As military low flying normally only takes place during the working week, the service is not available for weekend flying. There is currently no other way of raising a NOTAM for routine BHPA activities.
Historically, there has been a belief that raising a CANP or NOTAM for a site would attract military or GA pilots to come and have a look at what's going on. I can't change this belief except to say that there is absolutely no evidence for it. There is, however, evidence for near misses at sites where a CANP or NOTAM has not been raised.
Save a link to this form on your desktop or mobile device and the whole thing can be done in less than a minute. Then you can put the kettle on and pat yourself on the back for helping to keep yourself and your fellow fliers safe.