aristobrat, many thanks for the idea. I was thinking 'can I fit the AE into the system and just use the homehub as a modem and let the AE dish out the internet.
Yup, you could still do that.
I've never used a homehub (in the US, the routers are almost always separate from the modems), so I'm not sure if you can turn off the router features of the homehub.
If you can turn off the homehub's router feature (and just have it act as a modem), then you'd be fine just setting up the AE following normal instructions. Forget anyone every said bridged.
If you can't turn off the router feature of the homehub (so it's going to act as a router and a modem), plugging the AE into it and setting it up like normal means you'd have two routers in your house.... the homehub (which is plugged directly into the Internet) and the AE.
The problem you can run into with two routers in your house is that computers connected to the 2nd router (the AE, in your case) can't open up ports needed for some programs to work properly (like BitTorrent, video chatting, some games, etc). The computers all assume that the router they're talking to (the AE) is directly connected to the Internet, so they'll open the ports on that router, but that's pointless, because traffic in your house ultimately comes in and goes out thru the homehub. The ports have to be opened there for everything to work, and computers connected to the AE won't be able to do that.
So one solution to that is to setup the AE in bridged mode. That's a simple setting in the Airport Utility config program. This tells the AE to not act as a router. Instead, it simply lets wireless devices connect to it, and it bridges the traffic up to the router, which would be the homehub. So when your computers need to open ports on the router for programs to work, they'd be opening ports directly on the homehub, which is where the ports should be opened.
This is probably way more info than you wanted, and if you're never going to bittorrent, etc, it's probably not worth the time to setup the AE in bridged mode regardless. But just a heads up in case you don't used bridged mode and run into some issues down the road, you can look up this thread and see if it makes any sense then.
