Helmets

This might seem like a silly thread but I did UTFS.

What sort of helmet would be best for general mountainbiking, I wouldn't like to tie myself into a discipline.

I have a bmxing/skating style helmet which I use for my daily commute plus any racing and spins I do, I like it but would it be ok as a general helmet?

I have been advised to go fullface when I buy a new helmet for what my mates do, good advice?

Should I wait and invest in something with a detachable chin guard for more versatility?

Thanks!
if you want to know the answer to these apparently stupid questions I suggest that you join a club and go on spins..nobody is really going to give you real answers on here until you've paid your dues and they've seen what you can do.
Ok cut out all the questions that I need to know to people for them to answer, will the helmet I described be ok?