... you could do a lot worse than taking a look at the British Rotorcraft Association website at
www.gyroplanes.org
In the UK gyros operate under Permits to Fly, which are generally administered by the PFA (some are dealt with direct by the CAA). There are a few approved designs which can be amateur built under the supervision of the PFA, and one factory built machine (
www.rotorsport.org) with other designs in the pipeline. If you want to build a new design then it must comply with BCAR Section T (downloadable from the CAA website).