Which license to use?

[David Woolley]

> they must be assigned (possibly jointly) to the company; following the

I've never heard of joint assignments.  I think you would definitely need
a lawyer, and probably an accountant, in that case.  My guess is that, in 
the UK, the result would actually be that the license was assigned to 
a trust with both parties as trustees.  I think that would mean that the
licensor for the different parts of a composite work would, technically
be different.  IANAL a lawyer and the only advice here is that you would
need one in this case.

(If a couple jointly own a house, the actual owner is a trust.)