If you use over 10W, the new OFCOM rules on EMF may apply to you, especially if you are investigated over complaints by neighbours. As a QRP man, I am not bothered!
If you have a big tower, beam and full power you may have issues. You have to show that people can't be harmed by excessive EMF. If I had my way, all UK licencees would be limited to 100W, or even 10W!
See the OFCOM website for more details.
I quite like the Eire approach. In Eire, amateurs have access to much of the Band 1 spectrum. Why not grant all UK radio amateurs access to big chunks of spectrum at, say, 100mW ERP on a strictly non-interference basis? If you cause interference you get closed down, otherwise carry on. Oh silly me, this requires people with brains!!
Personally, I'd like access to some VLF spectrum and 40MHz. I guess the main issue is military access. I still don't understand why so much UK spectrum is reserved for the military when most is unused for most of the time. Views?