First post here so forgive me if I ramble

I'm at a bit of an impasse with my neighbour over his beech hedge. The hedge was planted double width by the previous owners (approx. 10 years ago), right along the boundary line. This runs down from the side of his house to the pavement, our drive is on the other side. When we moved in (5 yrs ago), the hedge was 3ft high and could you see over and through it.
The problem that we have with the hedge is that his house is on the corner of a T-junction and the hedge obstucts our view of the main road traffic and cars coming round the corner, which makes getting off our drive 'interesting' at best. I have spoken to him previously asking whether he would trim the hedge, only to be told 'that he has no plans to cut the hedge, but if i tell him which bits need trimming he will do it!' Unfortunately, his idea of trimming tends to vary on which bit of the hedge he is doing - his side and the front is about 1ft lower than when it gets round to us - and he barely removes leaves from the front which is the bit that really matters to us
Can i trim the corner of the hedge to make visibility easier for us? the hedge extends about 6ins onto the pavement. I have recently cut back the side hedge (our side), but this only makes access easier up the drive, not the view down the road.
Any advice would be most welcome. We are not at war, but do worry about losing the back end of our car someday. His car/driveway is not a problem to him as the garage is round the corner at the back of the house and he uses the back entrance to the house, so having a solid 7-8ft hedge surround his house is obviously not a problem

thanks
em