Great to hear you are considering constructing your own aircraft.
You will find this a really rewarding experience as you will be learning about flight and the engineering of such - at the same time.
Go to Oshkosh constructor haven. Pinch some tips and ideas from the Americans, do not have to uses all ideas only take what you feel comfortable with.
What I do say consider Levil for your instruments. (engine monitoring and flight)
Before you start get a grasp of the engineering principals as you will have a truck load of "experts" offering advice. Yes, they are every where, the best question you can ask them, "Lets go and have a look at your plane so I can see how you did that". Hmmmmm gone in the dust.
A very good place to start Bill Whitney has a set of CD's, get the CD's and the notes to go with them, then you will be on the road to happiness. Bill is an engineer who has a passion and an understanding these small aircraft.
KP