Steve Anderson wrote:

Thanks for the reply,
During the time I was building the run off trench the soil got a good
turnover and was left bare for at least 3 weeks while I was away
working. By the time I got round to laying the lawn it seemed fine.
Then the lawn lasted maybe a month or so then started to show signs
of dying in patches yet again. We live in Aberdeen and that was a
particularly heavy month of rain even for here.
It's interesting you mention grass types that are more suited to
wetter ground and shade as the area of lawn that always goes bad on
me doesn't get the sun. As you say perhaps another kind of ground
cover may be the answer but we like have a little grass and certainly
don't want to have a concrete jungle! I also thought about astro turf
but it's an expensive alternative that would still need proper
drainage.

If it doesn't get any sun, most grasses are unlikely to survive. If it's under
trees, there is a lot of competition for nutrients also. If you are in Aberdeen
WA, you likely will need to compensate for acidic soil conditions also.