dave wrote:
A bit OT (possible neigbour problem with their tree) this but would
appreciate advice. They have mature ash tree that's about 50 feet
from our house.

there is a stand of 3 ash trees 30 feet beyond the end of my garden (60m
from house!)

Last winter I dismantled the redundant kids play area and removed the bark
over textile safety surface. this was 30/40 ft inside our boundary. the soil
surface below the textile was criss crossed with ash roots and on digging in
preparation for lawning there were numerous hosepipe thick roots crossing
the area and heading deep into the garden.

WELL beyond the usual rule of thumb "roots reach as far as the crown"

pk