iPhone 4S iOS 6.1.3 will not connect to or even find any wifi networks, any ideas?

I updated my iPhone 4S to iOS 6.1.3 and therein started my wifi problems. At first the signal was just dropping out and I kept getting the "Unable to join..." message, which was annoying but it had periods of time where it worked fine and gave me some hope. Since yesterday my phone has not actually identified any of the available wifi signals (not just my router, but also any other networks when I've been out and about) and so I am unable to join any as I cannot even see them to select them.

I have tried:

- changing the channel on my router

- turning my router off and on again

- turning my phone off and on again

- plugging my phone into the computer and making sure it was updated (I did this yesterday which may have made it worse as that's when the problem intensified?)

- resetting my phone by holding down the home and power button

- resetting the settings on my phone (numerous times)

- changing the WPA2 settings on the router

- checking that I have got the wifi turned on

- setting my iPhone to "ask to join" wireless networks

I would suspect something fishy with the router, except that my husbands iPhone is still working fine (he has not yet updated his iOS), my MacBook and his laptop are still connecting fine, as is the PS3 and the wireless printer. I went out today to a place with an open wifi network and my friend with an iPhone 4S (*not* updated to iOS 6.1.3) could see it and connect to it, but my phone didn't even pick it up and we were sitting right next to each other. There are 10 wifi networks in the vacinity of my house which my MacBook and husbands iPhone can see but my phone is now not seeing any of them. This HAS to be something on my phone, but I can't ruddy well work out what it is and meanwhile I am going to get charged loads for using up my data allowance. The only good thing so far about having all this faff is that when I updated to 6.1.3 my phone wouldn't send any photos to anyone unless it was via iMessage and since I've been changing all the settings I found one that works, so I have been able to send my mother in law some pictures of her granddaughter. My own parents will be getting upset by the lack of wifi though as I don't want to FaceTime them using my 3G.

Any help would be most appreciated.