Hi Ray, thanks for your reply.
I have seen that blog post, would I be correct in saying that I need to…
# replace the following triacs http://rayshobby.net/wordpress/wp-content/uploads/2013/04/IMG_2623-300×168.jpg with a 2N3904 transistor
# swap my 24v AC to a 12v DC power supply
Last few questions…
# I only plan to power one solenoid, would I need to replace all triacs?
# The Pi will be happy with this setup?
Thanks for your help again, the world of triacs and transistors are very new to me 😉