http://www.edimensional.com/index.php?cPath=24&ref=73
is where I got mine from - use select currency button to change to £ - it ships from uk
my reviews are here
http://www.airwarfare.com/AWX/features/index.htm
and cover from basic tir3 to tir3 + vector expansion to finally tir 4
my advice would be to bite the bullet and go for tir4 as it is worth it
The vector expansion, included in TIR 4 or an addon for TIR3, allows you to lean left and right as well as back/forward and up/down and this will be supported in BOB - it isnt supported in IL2 so you cant lean round posts but the tracking is improved when you use the vector expansion. It is all explained in the reviews or on naturalpoints web site.