Thanks for your reply.
I think I have sorted it and you are on the right track.
By default the wifi connection should be closed when the screen shuts down, there is an option in the advanced wifi settings to select, 'Keep wifi on when screen times out'
This had been ticked, I blame my missus who was having a play with it last month, (the phone that is)
Now that is unticked the connection is closed whenever the screen shuts down, you can see the wifi signal icon blanked out when you reactivate the screen for a couple of seconds before it re connects. Have tried it like this for past couple of hours and it seems to be working fine.
