Before committing to buy anything like that you really need to try it out. The hedge is going to be the real problem and even at 5Ghz could be a major obstacle.
I've been back on site today, in the daylight and have a better understanding.
The hedge is a thick conifer of about 8ft to 10ft tall, so going through in not an option. There's also a number of trees in the why of the ideal route, but have found a clear line of sight route
It's not ideal, as it's going to have to run off a homeplug (I always prefer to run from the source if possible), but there's a clear line of sight covering a distance of about 25m.
So should all run without a problem