u can UV the head seperately from the body. but be aware of discontinuos UV border. u will need to do some careful clonning to get rid of it, and careful to not have any bump on the surrounding uv border for the bump map. unless u need it, then again careful painting for those areas.

- if u r modeling for film rez, there should not be any poly limits. :p

u can always create a low-low rez stand in version of ur model, it can even be simple cubes shaped closely as ur mesh.