Thanks for all the replies!
I am looking to scrounge parts as good steel is quite expensive. Might find most or all of in the scrapheap at work as high quality tubing goes in and out of the plant here all the time.

What kind of bags can be used when heating? Regular polyethylene would probably melt?
I am also curious how you set up the bags with the venting valve?? One pic probably say more than a thousand words at this stage.

How much pressure can you use if doing a wet layup? More than 2 bars and I was told the part would be resin starved.

I am not saying we are going to do this, but the idea is ricocheting around the inside my skull. I am a bit wary about having a homebuilt pressurized autoclave in my basement, but as long as my wife dont know..