Hi Hucklev

I think the answer to your question is that at least to start with IOSH would have you join as an Affiliate.

Then the question is whether they still consider your previous qualifications to be valid in the context of the Membership ladder. 

Your IOSH membership journey | IOSH

+ a consideration of your experience, but that's probably OK.

Can't remember when the numbering changed but your fairly old NVQ Level 4 might be equivalent to a Level 6 now so you might be eligible to jump from Affiliate to Certified.

Alternatively if IOSH don't think your NEBOSH Certificate is beyond its sell by date, then possibly a move from Affliliate to Tech.

You MIGHT wish to consider the recently added "Experiential" Route that bypasses qualifications.

However, that comes with a sizeable price tag and I don't know of anyone who has tried it as yet.