The BP Petrol Station on Huntingdon Road

So I have frequent cause to ride down Huntingdon Road. I'm usually doing so at a time of day when the traffic is heavy and slow. This usually suits me fine except for when I'm passing the BP Petrol Station.
As you will note from this close-up of the exit, there are no signs warning departing customers to look out for cyclists.
The big problem comes from the slow moving traffic. Since they're moving slowly, they tend to flash cars to join the traffic. EVERY time that happens and I'm in the painted mandatory cycle lane

1. The flashing (snigger) driver doesn't look for me
2. The emerging driver doesn't look for me
3. I'm going downhill at well over 20mph
4. I have to skid or swerve to avoid the emerging car

Now I've tried yelling at the emerging driver and they ALWAYS defend themselves with "But he let me out!". Of course (as irony is everywhere) I've tried yelling at the flasher and they ALWAYS defend themselves by saying it's the emerging driver who should have looked for me.

So I did some Googling and the legality of this is astonishing. Any collision would be (mostly) my fault! There's the 1973 case of a bus who pulled over near an emerging side road (to alight passengers, I think) and the bus driver flashed a car to emerge whilst the bus was stationary. The bus driver then saw an approaching motorcycle and started flashing and beeping madly to get everyone to stop. The car carried on out and hit the motorbike. The emerging car was found to be 1/3rd to blame for pulling out but the motorbike was found to be 2/3rds to blame for not foreseeing that the car might pull out!!!

Well since I cant get the cars to either notice or yield to my right of way, I thought I'd try & get BP to at least help by putting up a sign. Firstly BP told me that they don't actually own that station,someone else does and licenses the BP petrol sale rights & livery. So they passed on my request to the legal owners / managers. They declined my request saying

• It's the County Council who should put up signs
• A sign would cause a hazard & block the emerging drivers view of the road
• Shan't! No, no, no, I don't wanna, go away nasty cyclist!