Red obstruction lights in the UK
 

I've noticed a recent rash of new red obstruction lights appearing on a range of structures (cranes, chimneys, etc) in Britain that previousy were less lit, or less obviously so. Has there been a recent change in the regulations on what needs such lights ?

Probabaly just an insurance cop-out driven by the increasing litigation-happy society we live in, premium mitigation and/or liability limitation should something hit the structure.

CAA impose a min height above which OL are mandatory (lest all buildings and telephone poles and such end up with OLs) However it would make some sense to fit them to power transmission pylons, culprits for many an accident - glowing corona isn't visible enough ! But hopefully not the strobe discharge lights as seen on some TV masts !

Obstruction lights
 

These types of obstruction lights are regulated by FAA and ICAO, there might be a possibility that Aviation department of your locality have amended the rules for intensity of obstruction lights mounted above obstacles. Good quality of these kind of lights can be found at Aviation obstruction lights.