All RAF aircrew have to undergo aviation medicine training every 5 yrs at the CAM (Henlow), sometimes this training includes experiencing decompression, depending upon the specific role of the aircrew involved, and the mood of the instructors. They do not, however starve you of oxygen until unconsciousness, merely long enough to notice the effects.. .. .I have no idea whether or not they offer courses to paying guests, but it's not at all out of the question. Have a look at the RAF website to see if there's any contact details.