joe,
i also got two of the 40L kegs from boags.
i cut the top out and plugged the side hole with a tank fitting and bung.
so it can be removed if i whish to add a temp probe of something. plus it was easier for me to do it at home than take it to be welded.
i used a hole saw to cut a hole in the bottom, once again used a tank fitting, 1/2" threaded brass pipe and 1/2'" ball valve on that.
inside i've a copper pipe bend with the s.s. scourer to filter the hops etc. form the wort.
works a treat.
my only complaint, is that the barrel shaped ones i have, make the outlet angle downward.
but sat upon brick edges, not a problem.
i'm still trying to borrow the work camera, hopefull this weekend, and i'll post some pictures and assemly photos.
cheers
crackers