Always use the word crem. Less of a mouthful than crematorium
Probably depends how many funerals you've been to at one before you start to use it as a word, mind.
More affectionate in a way, crematorium seems very much colder than crem.
But that's just me.
Anyway, turns outthe lad i knew who completely re-arranged a girls face and tried to rape her at new year had also previously been charged with child abuse and child rape.
Also his mother and sister kept this fact from his other, eldest sister, who has two kids. She had to read about it in the local rag as a comment in the story about his being sent down.
So that's lovely.