How can I get back to the previous OS on my Z10?

I have installed the latest OS update on to my Z10.

Since installing this about 24 hours ago I have had major issues. My phone has been loosing its network coverage all day - only a reboot has resolved this, however as soon as I have made / received another call or text it looses its network again. This did not happen prior to the update. My network provider have checked and there are no issues their end.

My battery is very hot most of the time - the case on the back of the phone is too warm for 'normal', guess this is due to the receiver trying to locate a network. Had to charge my phone several times in the last 24 hours.

Volume settings appear wrong - I have the volume turned all the way up, and 'sounds' set at high level too, but alarm this morning was barely audible.

I can cope with the alarm etc but I need a phone that will work and at the moment this Z10 is failing.

Is there a way to remove the software update? To restore it back to the previous OS?

Overall bitterly disappointed in this update as my phone worked fine before, and now its only appearing good for the bin!

Any advice would be appreciated.