Dell :: Inspiron N5050 Laptop Wireless Connectivity

Unfortunately, I'd been blaming the broadband at home and didn't realise this before my warranty ran out - on 30/12/12 

McAffee has been uninstalled and Avast put on instead, but still it is the same - it works fine when the lead is plugged in from the router - on Speedtest it shows download speed 3.13.  On wireless at home it works, just, but speed is reduced to 0.49 even though I'm sitting right next to the router.  Bring it to work and it can't see the internet to connect to it