First, yeah, they wouldn’t install a charger through Motability, because Motability only covers costs if you’re ordering a charger for a pure EV, not PHEVs.
It’s hard to advise on companies for installations, if you don’t mention where you’re located. Most companies only install in a radius around their base.
For chargers in general, i wouldn’t be too concerned about someone using it. He’d need to park on your driveway (assuming you have off-street parking, which is a pre-requisite for the charger/grant), which already would take some balls – and then, he’d need to stand there for multiple hours to actually gain something out of it. Not many people would do that. That being said, most of the “more advanced” chargers either lock, or are started through an app on your phone.
Our shortlist for chargers currently would be the Ohme Home Pro, the Wallbox Pulsar Plus (current favourite due to design/size, it’s tiny compared to others), and a Zappi. The Zappi makes most sense if you have solar panels (that’s its “gimmick”), because you can set it to charge only if your solar panels create a surplus etc.
https://wallbox.com/en_uk/wallbox-pulsar
Link to the Wallbox (you can also order there, including install).
https://www.smarthomecharge.co.uk/chargers/ohme/home-pro/
Link to the Ohme (same applies).
Both are controlled through an App that has to be paired to the charger (done at the installation of the charger), so only people with paired phones can charge.
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.