Have you had a word with one of your local parish/county councillors, your local police, or even your local road safety partnership? If you haven't, I would. The councillors might be able to help, and even put pressure on the council generally or even the police to watch out a bit more for you.
You probably know that the law in England & Wales, generally, is that if someone hits you from behind they are at fault. The driver in front is only at fault if, for example they've turned and not indicated or they've stopped too quickly and their brake lights haven't worked (provided that can be proved - hence the crash for cash scams). Therefore, so long as you're indicating and are slowing sensibly (and put your elbows out a bit when you're approaching a turn - as they say in motor racing) you should be ok in terms of fault. Going on from that, if ever I have a passenger in the car it is understood that their first job is to get the number plate of any vehicle that hits us, and otherwise we'd just sit in the car, call the police and hold our necks saying "Ow!" (even though my first instinct would be to get out and flay the other driver before the g of bang).
As far as cameras are concerned, I've had a Transcend Drivepro 200 for nearly three years (it's my second dashcam). It received good reviews in car magazines at the time, but, as with all such things, it was soon superceded. The picture quality is quite good generally, but it struggles with numberplates except for a split second up close (which would probably do in the event of a forward collision, if the other vehicle disappeared, and if hit from behind would at least show I slowed and positioned the car in a perfectly reasonable manner - hopefully) and isn't so good in very bright light or at night.
I am looking for a replacement though. The others mentioned above are all well and good. Frankly, I don't mind if the camera is visible, as if it means other drivers see it and improve their behaviour then I'd rather that than be involved in an accident. The Nextbase range that you can buy from Halfords, Argos, etc look quite good. The updated 412GW, 512GW, and 612GW all have better picture quality and the 512 has a polarised lens that's supposedly great in all lights. The only other one of theirs is the Duo, which obviously does both. Although I'm hoping and waiting that they'll soon update it and improve the lenses and picture quality, and then I'd definitely have one.