Gordon whilst I fully appreciate your suggestion, and I broadly understand your last sentence, I wouldn't have a clue where to start with building my own.
Its been over 10 years since I have done any electronics, (but its slowly starting to come back
I bought the PI-Face to see if i could drive some outputs via some Python, and eventually via http, and having proved this much to myself, the next challenge was to drive larger loads, and different systems, and relays seemed to be the simple solution.
I very much like the idea of keeping my "Loads" and my "Logic" on separate boards, and a pre-built board was just the ticket, so when i realised the board bazooka posted had opto-isolators i was even more convinced that this was the way to go for me.
I am keen to learn more about I2c and the GPIO on these little systems, but so far i am only a few days into my new hobby. I would love to be able to take your comment about the ULN2803 and turn this into a working project, but even if i had this working on a breadboard, my desire would be to get this working on a PCB, and that presents another set of challenges and difficulties.
It would be great if someone could build a compatibility list of modules with one another, because it can be a bit overwhelming as a noob