IMO, I wouldn't argue that you were not parked adjacent to a lowered footway. IMO, it's clear you were. The standard construction pattern is kerb, single sloping kerbstone then lowered footway. Over time stones move, but there's no point arguing that it wasn't a lowered footway to the standard needed, IMO it was.
And everything in front of your nearside front wheel was adjacent.
But lowered doesn't mean 'dropped' as defined.
IMO, you do not have a two-pronged argument, yours is based upon a simple argument i.e. the condition of the lowered footway indicates that it has been in situ for some time, GSV shows it predates 2008 and that
'the purpose of assisting vehicles entering or leaving the carriageway across the footway, cycle track or verge' does not subsist where you were parked being delimited, you submit, in law as well as practice by the presence of fixed barriers at the back of the footway which prevent use for its original purpose at the point you were parked.
It was probably installed to afford access to the off-street commercial premises and