I know that the rated speed will not be reached but unfortunately I do not intend to rearrange my home to suite a RPi4 even if it stood a chance of improving things.
Since my last post I have tested all the various bits and plugging a laptop in rather than the RPi4 I can get roughly 20 times the speed. Jut trying to ping the Pi now results in half the packets being lost. I cannot access it either via my Windows PC or my Linux Mint PC. I'll try a fresh install.