One tip perhaps, mark it on your chart with a permanent marker pen. It is not just the southerly parallel bit, but the wide bit at the north end as well.
I approached it at 3500ft from the north, after missing Warton MATZ, and the 2452ft Radio Mast, thinking I had about 6nm to go, when I realised I was over Wigan with just one mile to go.... The old Cessna held together well in the ensuing dive....
These days it is 1300ft on the Manch QNH., and yes Liverpool (and Manchester) are most useful for class D Transits, as long as you are not crossing their Glide-Slopes.