Persimmon homes verge signs on Thame Park Road

Persimmon homes have put up a number of signs up on the verge. They are obstructing the view down the road when I leave my home and I can't see cars coming. Also one goes from the hedge to the road, forcing people to walk into the road when walking into town, as before there was space to walk on the verge. This has been an ongoing problem for months, at least 6 months. I would like to know if Persimmon home have permission to put these signs up or if they don't. And if not, can I remove them and return them to Persimmon homes. I feel that this is a real safety concerned and a accident waiting to happen. As you can see from my photos cars are almost completely obscured from view,when as before I could see much further. I would be great if you could let me know as soon as possible about what can be done. Thank you.