1. They don't, or rather, there aren't any 11n devices available. It's a huuuuge London house, with pool, belonging to a lady who is dripping in money. It's quite obscene, but that's another story.
2. Oh. I clever.
No they are getting to the router via a switch. Shirley that shouldn't make a difference though?
Loads of DHCP addresses free at the router. Originally I set the WAPs to fixed IPs, in the same subnet as the rest of the LAN. Then I read in the Buffalo 'documentation' that one of the devices should have a DHCP address, but whether that means exactly one, or at least one, or up to one, who knows. Anyway setting one to DHCP made no difference.
The docs also insist that the same WEP key is used (fair enough) and the same channel. So it forces you to disable auto channel selection before you can enable WDS.
Once you enable WDS you have to tell all the devices about each other by entering the MAC addresses of the WiFi interface of each device, into the config utility for every other device. (It was actually 5 WAPs so I had to enter 20 sodding MAC addresses, and after each one the damn WAP insists on a reboot which takes around 30 seconds, before you can enter the next. One of the WAPs should really act as a WAP-master and program up all the others. Sigh.)
The docs also say you should give the WAPs the same SSID, also fair enough.
There is no MAC address control (yet) on the WiFi network.
One thing that confuses me is that the WiFi side of the WAP doesn't seem to have a settable IP address, just the ethernet side.