Question 1: Which TARDIS? The BBC has changed the look of the Police Box over the years (see below). Looking around I am settling on the 2010 Matt Smith era model, which has the upsides of being a good throwback to the original and the most current as of build start. The downside is its also physically the biggest TARDIS yet.
Question 2: Scale. To build it full size or scale down. The advantage of a scale model would be ease of transport and cost, however I want this to be a usable 'garden shed' when done so even scaling down to 75% would make the door shorter than me. Actual size it is.
With these two questions answered I have to start googling around for plans (proprietary BBC, but you can find them on the net) and an online community to help. So far TARDIS Builders looks like a good resource.
I expect this ti take me a few months so if you are interested, check back here for build updates.