Is it possible to go on factory tours of F1 teams and maybe even see the wind tunnel etc or do you have to join the teams membership?

Grand Prix Tours has a factory visit (Williams to the best of my knowledge) as part of their British GP package. They also have Maserati factory visit as part of their San Marino package or Monza package.

Furthermore, those attending the sale will have a rare opportunity to visit the Ferrari research and test centre at Maranello - normally a restricted access area.

If you subscribe to the supporter's club membership with Sauber(which costs well over 1000CHF) you will have such a walk plus some paddock access, it is very good if you are someone who is attending a lot of GP and has that bit more money to spend:) Plus you will receive a lot of merchandise:)