BRITISH MIDLAND, as it was then, operated LHR - LPL in the late 80's & early 90's using the old Diesel 9's.
It was DC-9s for a while, but then worked down through ever smaller aircraft types. IIRC it ended up being operated by Saab 340s.
Even from North Wales, to the west of Liverpool, it is easier to get to Manchester Airport (just stay on the M56) than to Liverpool (turn off through Runcorn and Widnes on normal roads). Hence why Liverpool had such low passenger numbers until Easy started to operate a style of service just not available at Manchester.