Thank you for the feedback. To give you an idea, the little aerial gave me 100 miles easily as I am at 200 ft with a clear line of sight East, West and South. The new aerial was installed at 18ft, above my roofline and the spikes to the North were higher aircraft.
I have been 250 miles + for over a year, the drop has been in the last 2 weeks so I can only conclude that something technical has changed.
I would not buy a proper external aerial and mount it in a higher position to get less distance than the small aerial that comes with a radarbox. I work at an airport and everyday I could see what was taking off from Aberdeen, Edinburgh and Inverness within minutes of take off, which I cannot now.
Its not my imagination that something has changed. Can the aerial short in inclement weather and reduce its effectiveness.