On Saturday, 6 February 2016 09:38:07 UTC, Another John wrote:

Back on topic: Mathew: One of the first things I'd have done is email
those pictures to the people who make the lawn (seeds?) (I've forgotten
- you did mention the manufacturers in your first post). They after all
are the real experts in lawns.

I took your advice and got in touch with Rolawn. They even passed on my photos to the Sports Turf Research Institute and they both believe, caveated by the limited information to go on, that the primary issue is a leatherjacket infestation.

The mild autumn/winter has been suggested an aggravating factor and they have suggested a nematode application once the soil warms up. I plan to do this in April and will also apply in Sep/Oct when the new eggs start to hatch.

I plan on looking at drainage too and will post back tomorrow with a drawing to get thoughts from the panel!

Mathew