Hi everyone
New short one fitted and looks good ie its the correct diameter at the base. I don't really listen to the radio but the reception after a brief test was fine - no issues. On balance I prefer the classic aerial as its gives a feeling of movement from the slanted fixing. However as I keep clipping it in the garage, which is a bit tight, the new one looks good, modern in style and does not get caught or trapped.
As so often with the 124...the choice is yours.
Thank you everyone for your advice and links, always appreciated.
A