Hello chap,
I purchased my OT when full of ale after one of the cads and bounders on this forum posted an link for a £49 end of season bargain. I have been utterly delighted with it, the upgrades are bell and whistletastic but not worth the extra lucre imho.
Many folk advocate the ash catcher, but I have never noticed any ash blowing about the garden with my simple set up.
Buy the basic all the extras can be added save for the lid thermometer, but as I read another site today the author remarked that he seldom wishes to eat the dome lid so doesn't really care what temp it is

Cheers
Tiny