Wi-fi not working...at all!!

Hi..

Been having problems with wi-fi connectivity for the last few weeks, before ios 6.1 and now after too... my 4S will not connect to any wifi network at all, even tho the home pc connects fine.. sometimes works very briefly, but more often than not, just dosen't work at all.... doesn't pick up any network

I rang EE a few days ago, all they told me was to hold home & power buttons down for more than 10secs, wait for it to power off then on again (didn't work), and it should be fine... if not, ring apple...!! Well, that didn't work at all, and now the wifi tab in the settings menu is greyed out so I can't even turn it on if I wanted to...!!

I've just reset the network settings thinking that may do something, but no joy....

Help....!!!??

Forgot to add... on the very odd occaision that it does work (it picks up our's and others in the neighbourhood), if i try to connect to our wifi, i get an error message saying "unable to connect to...." so i dismiss, then it asks to retry, and so on.....