The biggest problem is that you are in rented accommodation. This will probably be more of the limiting factor as to what is possible.
Take a look at Homeseer for the system and then Z-wave, Insteon or even PLC-Bus And at a push you could use X10, For the modules.
Automatic/voice blind opening/closing
Remote controlled/voice activated lights
Music streaming could be done via Sonos. and there is a Sonos plugin for XBMC.
Video streaming - Using unRAID + XBMC (I have a dedicated media center connected to my TV)
Music streaming through the rooms including bathroom
I think you have answered your own question as regards XMBC, though using wifi to access the server may mean no HD, from experience HD via wifi is a bit hit and miss and more miss.
Energy monitoring is possible. Various stand alone systems that can also interface to a computer. Is it electric underfloor heating or a wet system. Temp monitoring is possible as is intelligent control.
Energy monitoring - Monitor energy usage to help reduce it as much as possible. I already have 9w LED installed in every room + I have underfloor heating but I'm sure I could lower my consumption by using home automation (maybe weather/inside temperature monitoring?). Is it possible to monitor water?
Heating management - Exact temperature control via
Probably not unless Urnet do an interface to do this, and it will mean modifying or adding to the current system. At the very least you would have to take apart the monitor housing and look for the composite video feed.
Security Monitoring - I live on the ground floor of a block of apartments which has a camera entry system; is there a way to get this camera feed on to my TV? And is there a way to allow me to release the main door (magnet). Currently it's a push unlock button on the telephone entry system which is made by 'urnet'
You would need to integrate some sort of bar code scanner, so either when you run out you scan the label, or every time you use something you scan it, and set the system up so that it knows that 4 scans of item y means you need to order more.
Food - If I run out of a item of food I want to be able to add it straight away to a shopping list which I can split up to different shops e.g. Tesco for most items and Lidl for a few. The Tesco shop would be a monthly shop.
Yes but they are not cheap, at least 600 to 1000 pounds for a 7" screen hidden in a mirror so when its off it looks like a mirror and then when its on you see a small screen in the mirror. http://www.simplymirrortv.co.uk/prod...oom-mirror-tvs
Bathroom - Can you get a mirror which can function as a screen; so I could access the weather report for the day, read the news etc when brushing my teeth and having a shave
Doubt it. You may get some deals on some of the items.
There maybe more but I cannot remember. Is it worth waiting to January to setup? Do home automation companies have January sales?
Some other things to look at
RFXCOM for wireless systems.