Answers:
Re-pointing is between £60 to £ 100 per meter square.
£4000 on the highest price per metre
Build up of hair, skin cells.
clogged vent pipe
pipe corrosion
blocked further down the drainage system.
Check for leaks buy walking around the property.
check for water dripping over the edges.
check for water flowing away from the property.
check for gaps, between the drip edges and fascias boards.
check guttering extends pass the roof edges.
check that fixing are all tight.
I would cut the breathable roof membrane and install. i would then install plastic eve trays to the area where the felt is moving about.
No a 450mm chamber cover cannot be put over a 470mm chamber