Hi there! I have the same problem also. The problem seems intermitant as well, no obvious reason at all. It seems to have just started in the last few months. The router starts again if it is unplugged for a few seconds.
The router is about 5 years old and has had no probs previous.. Come on you experts, sort us out!! Regards.
I also had a very similar problem but is now solved. I am also about 3 miles from the exchange. Mine would drop almost every minute!
I noticed that the problem got much much worse after approx 7 pm every night. To cut a long story short it is to do with background noise on your phone line and similar such settings that are directly under BT's control.
The difficult bit will be geting BT to admit there is a fault as they line checked me at least twice with no faults found. Luckily my ISP was very helpful and could see my problem and that the fault lay with the line not with me or them so they eventually convinced BT to tweak my settings and then it was problem solved.