With immense thanks to David Fernseh for his advice and encouragement I have just for the first time built a frame aerial. The design I got off the 'net was a 25" wide one with 15 turns of wire which needed to be threaded through 69 holes!
I was somewhat sceptical of what a coil of wire could add to a receiver but indoors it brings Caroline up from a hiss in the background to a good useable signal. The mains hash seems to almost vanish.
At some time in the future I will make up a standard one metre square aerial but for now I am well happy
I tried to take a photo' to upload but for some reason the windings create almighty moire patterns which destroy the picture.