I expect the Signal to the exchange will be optic fibre,to your home most likely it will be copper,and as we know copper being metal brings with it resistance i.e. the longer the cable the more resistance hence poorer signal.i assume your with B.T. not Virgin,but there the same just that the cabinets are closer to your probpert. Saying the in Luton B.T. have done the same as virgin and installed local boxes in the streets,hence your "nearer" the optical fibre node.
Sony Xperia Z5 review: Hands-on with the phone which the Z3+ should have been