Basic idiots guide for this one CAA law.
You must have 200 PIC hrs and 25hrs on type and be current
Broadly the airport and aeroplane must be suitable for aerial work (licenced aerodrome, 50 hour checks, etc.)
You can not land away or travel more than 25 miles from departure point. It must be 'good VMC' (2000/8) and no 'tricky' flying. You need to have the same kit in the plane as if it was used for training (first aid kit, etc)
If you meet all of the conditions in Annex 1 (and it is a G reg plane) then that is it.
If you can't, then fill the form in to apply for an exemption. (see talkdownman's link for the details and the form)