The plans on thebeachcats is all you need, including the measurements for cutting all panels.
Gougeon bros. stopped building tornados a long time ago and I dont think they distribute/sell plans anymore. At the time they built the best Tornado available, but it was done in cold moulded veneers with an inside supporting structure. They sould their Tornado business to Jerry Houlton who continued for some time. Jerry Houlton was the same person who collected the information from many sources which is now on thebeachcats. He started out building in plywood, continued with cold moulding but Marstrøms boats got a reputation for being faster in chop so eventually Marstrøm became the sole builder. Note that the glass boats Marstrøm built in the beginning was no better than wooden boats as far as I know, but the sailors went for his boats after a while. A 1987 or later Marstrøm is built with pre-pregs and autoclaved and is structurally probably better than a wooden boat. Not neccesarily faster..
You can buy plans directly from ISAF in the UK, but the plans on thebeachcats are better in my opinion. ISAF sells the originals, but the amassed experiences collected in the plans on thebeachcats make them much better.

A wood Tornado can do well at national events, but sadly the Tornado class is very, very, small at that level. It is not the boat which is fast but the sailors, you know <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
I sailed in the Tornado class for several years, but sold the boat last year. Now we are building F16 Blades..

Before you decide on any model, you need to decide on what you want to do. Sail or build a boat for several months? Pretty much the only reason to build yourself is to enjoy the process. Unless you have built before and have lots of connections you will not save money, and you will definately spend a lot of time on it, doing lots of mistakes. If you just want something different to sail, buying something used is the way to go. If you want a clear coated Tornado, you can find them around for a song from time to time. At the time, you could not give away wooden tornados. But these days I see some announced for ridicilous sums.

Before getting lost in dreams about clear coated wood, think through why you want to build and see if you have the right motivation. If "money" and "looks" are on top of the list, I would advice you to buy something instead.
If you decide to go through "the process", you can get a lot of tips on models, sourcing parts, how to do it and support in the builders forum.