I am looking at installing automation in my home and would like some advice/comments if possible please - apologies in advance for all the questions, just have spent so long looking into this and am still unsure of route to go and don't want to waste money buying the wrong things

Firstly I am in the UK - as this I suspect will affect some of the answers

This is what I would like to achieve and where I am so far:-

Hardware/Software - thinking about homeseer or hometroller - may go for the hometroller but also considering building my own little mini PC for homeseer to run on

Lighting - want to control some lights in my house, can I just replace switches with z-wave or x-10 light switches? if so what are best ones

Sound - want to have sound in at least two rooms controllable from same place as all other automation items - so was thinking perhaps either Sonos or fitting myself ceiling speakers with an amp connected to hometroller (or PC running homeseer) - want to be able to play mp3's from itunes and also send sound from PS3 when watching blueray movies or playing
games - thoughts? better solutions?

Cameras - want outside and inside cameras again controllable from one place - was thinking IP cameras probably wireless for this?

Security - may also add movement (PIR) sensors to be used to trigger cameras recording and also perhaps to turn lights on/off - if this is possible?

Heating - want to be able to control my oil fired central heating and monitor temperatures inside and out- bit confused as to how I do this, can I somehow link something to my existing heating controls (Honeywell ST6400C) such as a z-wave thermostat - if so how is it done and recommendations on what to buy

Would like to be able to speak commands and also for it to be able to speak back to announce things etc

Finally would like to control it all from PC and iPad - so was thinking HSTouch with plugins etc to work with all above items

Want to try and acheive this without spending a fortune - it is only a small two bedroom bungalow

Comments/Advice please.......