Thanks guys, for now I think I'll use two level spoonfuls in place of a heaped one. In a marinade it's not going to make a lot of difference if I'm a little out anyway.
If freezing these chicken tikkas is this best done before or after cooking do you think? I suppose reheating cooked tikka may risk drying it out, but freezing raw marinaded tikka may lead to a watery result when defrosted which may shed too much of its marinade. Can't decide what the best way might be.