Thats a great point about midges I didn't think of that your right it would be impossible to sit out and enjoy the summer evenings if we were under constant attack by midges. Also the grass would be as much use as it is now and tbh I wouldn't even dare walk on it at the moment.

If I dig out the bed that the Lavatera is in and turn in plenty of rubble and sand about 30cm down would that be enough to solve it for now or would the natural water table just fill it back up? I could put it in a pot for now but would like to get it settled in a nice spot in the garden as looking at pictures on the web they look fantastic when established.

As for light when the extension is built we do risk loosing it all with the hedges but its just a factor we will have to live with it would be nice to have the sun but there has to be a comprimise. Finally in your opinion will my laurels be at fence height in about 5 years?