Map Application lost its accuracy on iPhone3GS

I got the phone in Feb2010 and the Map GPS standard application was completely brilliant and accurate in several countries for navigating from address to address.
The best thing about it was the way the current location blue dot updated very swiftly on the move. If you went wrong you could easily see where you were and get back on track.
Then about November last year the current location blue dot started getting stuck ( here in the UK) and it has been useless ever since.
Basically it never now gives an accurate location but always shows the current location as being several streets away from where I actually am, whether it is at home or on the move.
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Question: is there anything I can do about this? I have completely recent updated to the latest iPhone software and it makes no difference whatsoever to this particular issue.
Thanks in advance
MS
PS - does anyone recomment any good Apps that have exactly the same style as the standard iPhone GPS App. I really find the blue dot relative to the route the most useful way to navigate ( as opposed to your Tom Tom or Garmin type step by step instructions to get you to your destination)
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