I had an upgrade to Android 5.0 this week and since then I have had conenctivity issues. If Im at home using the Wifi its fine but if the Wifi goes down, or if I leave the home or just switch the Wifi on it doesnt revert back to 4G.

My girlfriend has the same phone and had the same upgrade but doesnt have the same issue. At the moment I am having to restart my phone for the 4G to come on.

Any suggestions?

Try wipe cache partition if that doesn't help try wipe data / factory rest.

https://www.youtube.com/watch?v=l6S6hRsNS2k

Thanks. Ended up doing the factory reset. What a pain in the arse. Ah well, it worked!

Myself and my girlfriend both have the same problem and both did a factory reset and it didn't make a damn bit of difference! I can only imagine it's a software problem given everything was fine before the Lollipop update!!

Try turning off smart network switch in wifi settings

This feature isn't turned on...