As a rule i will give new turfed lawn its first cut after aprox three/four weeks by doing so it should have had enough time to knit together, on its first cut dont go to short and the following cuts come down on each cut untill the desired height is achieved, julien.

I agree with Julien...he gives you the same advice we have been given by our gardener (new turf is going down at the end of this month). We were also told we'd need to water the lawn every day until it is well established (unless we have an abundance of rain of course) and not to walk on it for a minimum of 3 weeks.

Thats what they told me water daily cut after 3-4 weeks and keep off it till then. You are in Kent so if like me you are in drought you will need to water it for at least an hour every evening when the sun has gone. If you are on a water meter and it does not rain you may find it very costly.