Series 9 Different filming location.

In series 9 I noticed when the fire began at gaz and Donna's flat the outside location was different to previous series I visited Runcorn last year to do a two pints location hunt and the original location for the flat was Alcock Street 53.34199°N 2.73224°W but was changed to somewhere else for that episode, but confused to why they changed it and surprised that a avid fan like me wouldn't notice.