Perhaps a weathered Pycnoporus, but I'm far from sure about that. it's hard to say anything about this, given there's only a top view. Can you find out what the underside looks like?
Thanks, I just replaced the photos with some better ones showing underside on left. I also added a sighting of another orange fungus growing in cracks in a dead log - the phone camera gives its location as someone's front garden, but it was in the public open space at the end of Glasgow Place.
With a magnifying glass you'd see small holes on the underside (say about 5 per millimetre). Sometimes it comes out of wood first as an irregular 'blob' but then starts to develop into a shelf-like growth The upper side may become weathered with time (e.g. by becoming bleached or by gaining an algal or mouldy growth, so becoming discoloured) , but the underside generally keeps the strong orange colour. You see the genus on many types of wood.