Trader4 - Thanks for your reply. I will use the Autumn/Fall fertilizer as you say, mid/late September.

Yes, the grass is a mix specifically for the UK climate, see below it includes "Slender Creeping Red Fescue".
The Rowlawn site says ..............
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"Specifically selected seed type sowing mix Produces a turf that provides the most suitable performance for the diverse UK climate. It is highly adaptable to variations in rainfall,
sunlight, soil type, pH level and nutrients
"High content of Slender Creeping Red Fescue Extremely drought tolerant. High performance cultivar in times of low rainfall "
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Answer to questions please ..........
On my questions 1 to 5, I would appreciate a short answer to each if you could please/

1) Should I still look for a fungicide, do you think it still needs one?

2) Will the grass thicken up or is the dead bit dead? I want to get it back to a thicker denser, multi-bladed, healthy grass.
Is the dead part of the lawn at ground level actually completely dead in the roots, or will new grass push through to thicken it up again.
Can I risk scarifying it in the Fall or Spring to remove the dead stuff?

3) How do I keep weeds at bay? - where the grass is thin, do I need to top dress (seed/soilo/compost/sand) and when?

4) Approaching autumn/Fall - do I have to remove the dead grass? Should I put a treatment on it to feed it through the winter? { You Trader4 said "Yes, put a Fall fertilizer down in a month". I will use the Rowlawn Autumn Lawn Food.Autumn Lawn Food from Rolawn

5) What height should I mow at? - I have raised the mower to a 2.5" cut. It won't go higher. What height should I be working towards as 'normal' and by when?
Do I go for 1.5" during next spring/summer? Remember this is supposed to be a fine blade 'show' lawn.

Many thanks again for such a prompt reply.

Puppilup