He argued that there is little/no difference in level of difficulty in BSc/MSc (he says this from first hand experience), so there's little point in doing a BSc if I can get onto an MSc off the bat.
depends on the subject - if its more of an applied/vocational course then that could well be the case, there are also conversion courses ending in a post grad qual that are aimed at people who's undergrad was in a different subject area - some Computer Science MSc courses are like this and basically teach a mix of 2/3rd yr BSc courses
Why not just forget about the letters and look at both BSc and MSc courses - pick one that you think will be most relevant to your personal aims... maybe find out whether your HNC offers you any exemptions (in the case of BSc courses - could you skip the first year etc...?)
Is accreditation of some sort important in your area, if not at your current employer but at other potential future employers a few years down the line?