In the UK there are rules if you plan to use your UAV/Drone/RC aircraft for commercial work, but for recreational use there are no official rules for flying small UAV's, there are regulations for larger size ones, and some even require a airworthiness certificate before it can fly.
However here are the general guidelines for operating UAV's (the smaller ones we use in this hobby)
- Only fly Small UAV (under 7Kg)
- Do not fly above 400 feet (~122m)
- Do not fly beyond visual line of sight
- Maintain a "pilot in control", which is to say that you must always be able to take manual control and fly the aircraft out of danger
- Stay away from built-up areas
You can see some more details on UAV regulations/qualification requirements here. But essentially there are two operating cases depending on the risk factors. For Case 0, you dont need any qualifications to fly which are dictated by the general guidelines above.
Disclaimer Please note that the information that I provide may not be correct/up to date so its best to read the CAA rules and regulations yourself.