Thanks for everyone's input.
I will rethink my plan as the last thing I want to do is create something that will not be 100% safe. Let alone the risk of not complying with regs and rules!
It'll be easier to build a 30cm high deck and trim 3ft off the perimeter hedge so I can see the view from...
I thought we could just make sure there is a decent amount of timber under the fixings to secure to along with securing to the walls and that we would be enough. I think I have underestimated what's required!
I live in a rural location with only one neighbour and I am considering putting a roof terrace on our own flat roof that already exists. My neighbour has no problem with this but it would allow us to see over part of their garden so I understand this means we are not likely to get planning...