Certain things about the story stand out for me.
Firstly that it was late at night, or rather a Sunday morning in a rural area. Far be it from me to suggest that Kevin had been at a boozer somewhere and was on his way home, but he wouldn't be the first, I'm sure.
Secondly the bit about the cassette player. He says the player was on then he was baffled and threw the fascia out. Out of the window? An open window? A window left open to give him some fresh air on his way home late at night? Whilst he sang along to his cassette player? I do the same thing (apart from throwing things out of the window) when I'm on my way home late at night, to stop myself from falling asleep at the wheel. I bet I'm not alone here, right?
I'll not proud of it, but I'll confess that it hasn't always worked and I've jerked back into wakefulness with a start, heart hammering as I find myself belting down the road ("faster than I should have been"?), crapping myself at what I've allowed to happen and thanking my lucky stars I'm still in one piece. Sometimes it has been the appearance of someone running out in front of the car that has startled me awake, or large animals, typical hypnagogic hallucinations.
To me Kev's story sounds just like he fell asleep or was falling asleep at the wheel, perhaps after a couple of sherberts, and woke suddenly, befuddled, as he travelled a stretch of road which knows has had at least one recent fatality (he also states that it happened just before "a very very tight bend"). I think his unconscious mind was shaking his conscious mind back into full control before he hit that tight bend when it would have been curtains for both minds!
Add to that the fact he thought the face was there for 40 or 50 seconds during which time it seems he threw his cassette fascia out. This sounds strange to me. Did he throw it at the face, or as I interpret it, just out of the window? If you saw what looked like a person at your window at such a time, would you throw your cassette fascia out of the window, or brake hard? To me, the appearance of a face by the window at speed would trigger an immediate jamming on of the anchors in a normal, wide-awake sober driver, throwing something out of the window is just not natural, even if something has terrified you. I know that I'm falling asleep when I start thinking sentences that don't make sense, complete gibberish, and do things for no apparent reason. I've yet to chuck my tape player out of the window, but there's always a first time.
Anyway, I would imagine you'd get a bloody good look at it, 40 or 50 seconds is a long time - get your stopwatch out and see, more than enough time to be sure of what the hell is going on. Unless, of course you aren't fully awake.
You'd cover a considerable distance at 60+mph as well, can anyone local drive past the scene and estimate how far he'd have gone with this "bin bag" hanging off his wing mirror?
I think more interesting than the supposed ghost angle is the RAF transmitter which apparently prevents TV broadcasts. To me, the answer to multiple experiences in this locale is more likely to be related to MOD transmission equipment, secret or not, and some kind of electro-magnetics.