Manchester does still actually control up to 29K from an area from approx Birmingham up to Leeds and then acoss to the an area up to the Dublin FIR boundary. A sizeable block of airspace !
I believe this was done initially to assist London in taking some pressure off the busy airspace not just within the MAN TMA but for aircraft routing above Manchester in/out of Birmingham, Leeds and Liverpool IOM and Blackpool.
ie North of Brum, South of Leeds etc.
The Centre also handles a lot of mil traffic heading North out of Mildenhall which joins airways in the Manchester area, most Kc135s etc struggle to make 29K or above by Manchester on there way to the US.
As pointed out the Manchester centre sadly does however close next year when Scottish ATC will take over.