Just for info, the CAA define business aviation (which is part of GA) as non-commercial movements operated on aircraft of 2730 kgs MTWA or greater conducting business operations (e.g aircraft owned and operated by Multi-national companies). So many of the flying school, private, or group movements are seen simply as GA and not as business GA.
They define air-taxi movements as a movement by an aircraft of less than 15MTWA operating a non-scheduled service, these services are predominantly sole-use charter operations. These would be included in any Civil Air Transport numbers.
It's hard to find any overall figures since this would require the CAA to do a census of flights. Clearly that would be a logistical and practical nightmare, although I remember it has been done in the past, possibly in the early 90's. But they can confirm that 235 million passengers used UK airports in 2006 (which does not include passengers who use UK airspace but do not fly in to or out of a UK airport). The number of movements to handle these passengers was 2.4 million (again, no account taken of overflights of UK airspace). That is a huge number of people and aircraft, and it is some of these who will be most exposed when there is an infringement occurring.
NATS recognises it is a potentially huge risk to its safe operation (and the ultimate safety of airspace users), hence the high profile campaigns and proactive measures being taken with all elements of the UK aviation industry (which includes GA).