Have a look at this (CAP393). It's a big document, but search for Rules 5 and 6 in Section 3. This will tell you what's allowed.
http://www.caa.co.uk/docs/33/CAP393.pdf
If you are disturbed by low flying aircraft, the best and quickest way to deal with it is to note the registration (which will usually be on the wing or else prominently displayed on balloons etc) and ring the nearest aerodrome. They will usually hunt down the miscreant and prevent a reoccurrence. There's usually no need for heavy action. All airfields want to be good neighbours.