Looks like I should be able to program hotkeys into my remote to control Skype:

https://support.skype.com/en/faq/FA12025/what-are-hotkeys-and-how-to-use-them

'Focus Skype' sounds very useful.

Hopefully I'll be able to set Sykpe to use the analog sound out and keep the rest of the system using hdmi audio out. We shall see.

Skype supports separate audio output device for ringing - good news. Bad news is I'd forgotten the HP doesn't have any onboard audio. So to achieve the 'always on' ringing I'd need to add a sound card into the spare PCIE slot. Looks like about £26 on Ebuyer

Skype hotkeys can only be Ctrl/Alt/Shift + key based, sadly my current remote doesnt support those commands. On advice from the interwebs I've added an infrared keyboard device to the Harmony "Windows Media Center SE" which should be able to send the required keys but for some reason my receiver doesn't respond to it. The receiver is MCE compatible so everything says it should respond. Not how to proceed.

Other than that, got a Logitech Lifecam which does a great job of showing the living room with a decent built in mic so thats a step forward.

What about a cheap USB sound dongle off eBay, that's what I got for my Microserver

That's what I've got at the moment. I've got no idea how to troubleshoot why its not picking up the (emulated) keyboard presses. I suppose I can buy another one and run 2.