Norwich's bill for "yellow jacket staff" is probably around £1M, most of them clearly superfluous.
It has very few 'large' movements and plenty of opportunity for GA. Only a total mug manager would try to exclude GA traffic. Everything is a fixed cost (ATC, the yellow jackets, etc) and the more you can get towards paying those the better.
Also the security is way overdone. The terrorists are not going to target Norwich. You could blow up most of that part of the UK and few people would notice. The obvious targets are .... more obvious!