I'd continue to park in the space if it's the only one available, but have a pre-prepared note ready to put in your own windscreen, along the lines of:
"The road is a public space and anyone is entitled to park here, as spaces are available on a first come, first served basis.
I too have worked shifts in the past and got home early in the morning, so there have been plenty of times that I have had to walk a distance from my car, but reserving of a space on the road is not allowed. At the moment, I am heavily pregnant and struggling to walk long distances. I park further away if I have to, but no-one's "need" for a space trumps anyone else's.
As with anyone, I will always park as close to my house as possible, but if you live in a property with no allocated parking or driveway, the risk of this not being possible is a downside to roads such as these.
I will not be parking further away, when a perfectly legal space is available to use, closer to home.
Please also be aware that "reserving" of a space on a public road is not allowed - see [insert government/council web link here] for more information. The use of cones on a highway also requires a permit."
I'd also add something about blocking a pavement from wheelchair or pushchair users, if he's having to block that too to allow cars to go past.
But, otherwise, I'd consider getting a dashcam that records any motion even when your car is parked, just in case, but also as PP have said, speak to your local PCSO and your local councillor.