Thanks for that, fihart - it was all the fuss about the iPhone problem that made me think it may be my issue as well. It's fine in my car even when only parked outside, because the hands free takes over and the 'phone can sit in the cupholder which, being plastic, doesn't affect it. I've tried a bluetooth dongle but I still have to touch the darned thing to make or answer a call. doubt the maker would do anything now - I put up with this since March of last year blaming O2 for lousy signal at home. Anywhere with a sufficiently strong signal still lets wnough through to allow for me touching the unit.
This sounds like the issue which has marred the new iPhone launch. They've run the antenna around the casing so that the phone works fine if you balance it on a table and shout at it but has a problem with signal when you actually hold it -- like a phone ! I'd go back to the supplier and see if you can duplicate the problem and demand a different model.
I've ordered a set of earphones on e-Bay because my own have gone adrift - maybe they'll help the situation. No point in looking inside to poodlefake an external aerial then?