The 5 x 142's which are going "Up North" were only ever on short term lease and were "loaned" from Northern Rail whilst class 158's were being refurbed. So what is actually happening is 142's are going back to the company where they belong and FGW▸ (First Great Western) are going to get some nice clean 158's.
Feel sorry for us northerners who have had to make do without these units for some time now