I guess you are right Onions, the sparkfun module does look a lot more user friendly, especially for a semi-noob like myself 
That's a good point about the Ethernet idea, I hadn't even considered that because I have not even got around to getting a phone line installed yet but that is certainly an option that I'm going to consider.
@Lurch, I know what you mean about the doorbell, I had an alarm on my old place and I fitted a door bell switch for a quick set when I went out the main door. I was thinking of something slightly different, though it might not work how I first thought. I also have one of these RFID proximity readers to fit http://www.tlc-direct.co.uk/Technical/DataSheets/Ade/TSSS01_Install.pdf they mention configuring the PTS input on the panel to accept a key switch input so I guess that would set the system? I wonder what protocol the 'comms' uses? Way out of my comprehension probably but it would be great to hack it to interface with an arduino lol.
That's what I thought, the factory units for telecomms are quite plus I would like the sense of achievement of doing things myself