I seem to remember the Friends of Strines Station website (sadly currently offline?) had a warning about cars being broken into overnight there back in April too. Both car parks have very inadequate lighting (I think Strines car park still isn't lit at all despite recent improvements) and of course no CCTV.
Given how busy it is, the Marple overflow is really not fit for purpose in any way - security, lighting, capacity and even pedestrian access across to the station once you've (literally?!) dumped your car is pretty bad. Needs Northern Rail, TfGM and Stockport Council to give it a complete rethink along the lines of Hazel Grove.
At the same time, WHEN are they going to iron out the ludicrous jump in Manchester fares from £4-something to £10-something (and that's off-peak) between Strines and New Mills? This would probably mean many Derbyshire residents could/would leave their car at home and use their local station rather than being forced to drive across the border and fill this car park... (I've no problem them doing that, they simply shouldn't have to for a "fair" fare). Current High Peak MP and local councillors sadly don't seem to see or understand the problem.