This is a widepsread problem.
An article in the paper the other day reported that residents in the Ribble valley had this problem
A web site says it is common in Cheshire and the Wirral.
My Thomson set top box sorted the channels, on the second attempt, and it has BBC1 (NW) in position 1 etc. The Panasonic TV has the Welsh channels in 1,2,3,& 4 with no chance of sorting them.
I do not know if a new, more directional aerial, will help but it would be nice if someone, or organisation like Digitaluk, offered some solution to the problem.