507 021 was on Birkenhead North Depot last Wednesday (16th). I saw it from a passing train about 13.30. Obviously been moved from Kirkdale at some point.
Incidentally, 507 008, caught on the Southport line the same day, is sounding particularly “loud” at the moment, it was almost deafening in the tunnels! Closest analogy is an MCW Metrobus with a bad diff (mmm… lovely)
other units seen the same day:-
Northern
507 - 002, 007, 008, 009, 013, 018, 023, 025, 027, 031
508 - 112, 117, 126, 128, 131, 136, 137, 138, 143
Kirkdale depot
507 014, 507 017, 507 024
508 125, 508 140
Wirral
507 - 004, 012, 016, 019, 026, 033
508 - 108, 114, 122, 123, 139
Birkenhead North Depot
507 015, 507 021
And finally saw 230 009 at Bidston at around 13.20 from a passing train, it was in the Wrexham bound platform
Best wishes
Chris