Hello, I am a solicitor with 20 years experience. I will try to help you with this.
It sounds a if yo may have been granted an easement (in this case a right of way) over the neighboring property here. If that is the case then the right attaches to the freehold interest of your land and burdens the land yo use for access . It is not a personal right, so a change in ownership will not affect your rights.
So does this mean that the new owner can not change the size/shape of the access land, as i believe he wants to change it to give him more parking space?
No, he can alter his land, but he can not do so in way that interferes with your right of way.
If he did alter the shape/size, what happens to the specific area cross hatch in blue on my deeds will this need to be amended to show the change?