Both Defender and AVG (and the inbuilt Windows firewall) are free, but combined, do they offer a same service that Norton does?
Also, Norton 360 is messing me about, not letting me turn "Auto-Protect" on.
Also, Norton 360 is messing me about, not letting me turn "Auto-Protect" on - Am I able to just get rid of Norton and use the other two?

I'd go the way you have and dump Norton without the slightest hesitation. You might want to consider Spybot S&D too, free to download, to deal with spyware/malware etc.

You can have as many anti-malware programs as you like, but not two anti-viruses as they'll fight each other.

i would uninstall 360,norton products are not up to much nowadays.having said that windows defender is rubbish too.

AVG with Firewall is all you need windows Defender is rubbish and Norton is at the stage they makers can't give it away it is also rubbish I had it on my PC in 2004 and a Trojan was sent to my email address and Norton never found it I had to download Spy Bot to get rid of the Trojan and Norton never even found it on my system after I spoke to a friend she told me in a conversation that I had a Trojan by the way my PC would not shut down. I purchased AVG with Firewall and never had a problem until late last year then I changed to Panda.

Avg is an anti-virus, 360 is also an anti-virus, you should never have 2 anti-virus programs. if you have stacks of memory and loads of space then Norton is ok, but it does use a lot of resources and does slow the system down. take care and good luck.

pretty much, Norton just does it all in one. small world, i use to use Norton 360 but now i use exactly what you do, only catch with free software is the tech support isn't as good as the commercial ones, for ordinary browsers like me, those two should be fine, just be sure to run a manual scan on both at least once a week, at different times of course and make sure they are both kept up to date.

Norton is a little more thorough, but defender and avg is fine on its own.

The only norton i'd say worth consideration is NOD

No, you shouldn't have two antivirus programs running at the same time...both of them could cause conflict with eachother. Windows Defender is good...AVG is reliable. Stick with those.