Fault finding on wireless and wired network

Question

My home network is proving very unreliable. Setup as follows -

Upstairs Office - All ethernet wired

• Switch connected to downstairs router
• Desktop PC
• Windows Home Server
• Oki Printer

Downstairs Wired

• BT Home Hub (central point for network)
• Linksys Wireless Access Point
• 2 x Xbox 360
• HP Printer
• Xerox Printer

Wireless

• Brother printer
• 2 x Dell Laptop
• Toshiba Laptop
• Android Tablet
• 2 x Windows Phone
• Android Phone
• Xbox 360

Think that's everything. I've put a diagram of it here if that helps.

I'm having various problems that I'm not sure how to attack.

1. All cabling, network cards and switchs are 10/100, yet some connections show as 10 only
2. The wireless devices struggle to hold a reliable connection. We've had them connected to various all in one devices like the home hub and none have been reliable. I've recently introduced the Linksys wireless access point to try and get a reliable connection, yet still I frequently (several times each evening) have the laptops lose their wireless connection. This shows as the warning sign on the network symbol in the status bar. The wireless router can still be seen but the quickest way to get the connection back is to disconnect and reconnect. This happens instantly and the connection is restored instantly. But it's happened with all wireless access points/routers we've had and all the devices (Toshiba laptop and both Dells) so I can't see how it's hardware related
3. The Xbox 360's sometimes lose the ability to see the media shares on the home server. When this happens the PC's and laptops can still see them, just the 360's that can't. We had this for the last week. Tonight the media shares suddenly reappeared when I went to have another go at fault finding on them.
4. The laptops struggle to connect to a file share on the home server. When you attempt to access the file share you can sometimes be waiting for 30 seconds to a minute for a directory listing to appear. You can even get the file share showing as unaccessible, despite one of the 360's at the time being in the middle of streaming a movie from the same device

Think that's all the problems. I'm a software developer with experience of setting up networks and servers etc, but not going right down into the nitty gritty of the set ups. I understand much of the terminology, but don't know which tools to use and where to start in trying to untangle this web and sort the problems. The problems that are most annoying are 3 and 4 currently, but I'd like to resolve them all if I can.

Can anyone offer any pointers to other posts/resources/books/tools that could help with fault finding this mess please?

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Never considered until now, but my Xbox 360 controllers are also proving problematic to connect. It takes a good few minutes for them to connect. Possibly a WIFI signal clash?