Ruddy 'eck!
Windows updates use a massive amount of data, which must be costing you a fortune via an O2 dongle!
Click the Start button.
Click on Settings
Click on Network and Internet
Click on Wi-Fi
Click Manage Known Networks
Click on the name of your network. (It might include 'O2' but it will probably be the only entry anyway)
Click on Properties
Turn ON 'Set as Metered Connection'
(If you can't find your connection listed via that route, go through the same process again but, instead of selecting 'Wi-Fi', select 'Ethernet'. It's got to be there somewhere!)