It's all about light kawechel. Cut the way it's been cut light doesn't get to the lowest part of the hedge. An angled cut let's light get down to the lower branches. Mind you conifers do suffer die back for a variety of reasons but yours is more than likely down to bad light.
Hydrangea petiolaris doesn't eat into render or anything it just clings to a wall. A good climber for your situation.
I'd let it grow out a good foot before doing any cutting. If you get some longer branches you can try pulling them downward to try to cover it. That's about all you can do.
I don't know what your soil is like nut but it's been very dry recently. Can't hurt to spray for mildew.
Welshonion it'd have to be a very tall dog to do that. The reason for the dieback is it hasn't been cut properly. Conifer hedges need an angled cut, wider at the base narrower at the top. You won't cure dieback just manage it or replace it.
You can use any of the water retaining crystals xyz, brand isn't important. The secret is to not let the compost dry out in the first place. If you let the top layer dry out it forms a crust which water won't penetrate. You can top dress a pot with grit which stops a crust forming, or use a plastic bottle upside down and sunk into the pot to water. Both work equally well.
Depends where you live Emma late April early May. New growth can be badly affected by frost.
It's arum lily tcam. You can dig them out or use a weed killer. It takes time to rid yourself of them they seed freely. Some people love them others not. Now is a good time to use a weedkiller if you wish.
It's bound too Charley give it 3 weeks for 2 ft.
Sounds like you have blackfly as well as green. Spray with an insecticide, rose clear, or mildly soapy water or continue squishing them with your fingers, !easy but equally as effective.