It was a new turfed lawn just under two years ago.
About three weeks ago I gave it a spring feed but my problem is some areas of the lawn seem to be growing well but other areas just isn`t growing at all.
The lawn has about 7-8 hours of sun a day with none of it has shady bits until the sun goes over the top of the houses.
The lawn is a good quality lawn without ryegrass and the soil is a good loam mixture but slightly alkaline at 7.3ph.
It is watered after about 5 days without any rain on it.
Can someone advise as to why some areas wont grow please?

Sounds like you've rules out lack of sunlight, moisture and nutrients. So it might be worth considering one of these:

*Soil compaction = poor drainage and poor root development
*Disease = problem would likely get progressively worse/spread
*Pests = there's a few different grass root feeding pests (eg chafer grubs and leather jackets)

If you have areas of grass that aren't growing due to one of the factors above, then adding a spring feed won't help.

Can you take a digital photo and post it in the gallery; it'll give us a better idea of what's going on.