LordofBiggles

If that happens again reboot the modem, wait 2 minutes, then reboot the R3, wait 2 minutes and see if you get internet then

Let me check before you order, I can try it this evening. Be advised, if you go with BT and have the 900mbps FTTP connection that's on PPPoE so you wouldn't achieve the full speed without putting your R3 in the DMZ of the BT hub.

Didn't think so but thanks for confirming, I'll let the team know again to see if we can get it resolved quickly.

I don't think it's been specifically fixed but I've given you Early Access just in case and so if it isn't fixed then when it is you'll get to try it as soon as it is available

If not you have to add this information on the general Company web that on R3 the ppoe connection max speed is 500 mb. 

As above, reboot the router then do the upgrade and it should work fine

If you haven't already tried this - try rebooting the router.  I always reboot my Netduma router prior to proceeding with an update. It seems to make things proceed more smoothly.  Then once you return to the router's interface see if you can get the update to proceed. 
Would also recommend factory resetting your router after you update ( Settings>Troubleshooting>Factory Reset).
Thanks.