It depends on what the employer is looking for if they think you are 'over qualified'.
Personally I think that's a good skill set.

Have you thought about a quality course?
http://www.thecqi.org/Training/

Or perhaps fire?
http://www.vulcanfiretraining.co.uk/

I have done training with Vulcan and would recommend them.

Hope this helps

Andy

If you are only looking for another qualification for the purpose of job hunting then it would depend on what the job spec states..

Sound's like you've got a few under your belt. Going off on a slight tangent, having had discussion recently around what your query relates to with peers and recruiters etc. (and based on personal experience) more doesn't automatically mean more successful interviews!

It's about how well you convince a prospective employer that you have the best skills for the role, and generally basing this around your achievements and skill set and how you can help the employer wins the day, rather than citing qualifications. I only say this as you've worded your post such that an extra qualification is a means to an end (a new job), and if this is genuinely the case why not invest in executive coaching or the like?

Environment (Unless you cover those in your various bits and bobs).
Most H&S have some element of E bolted on these days. Then Q and F and.....
Start with E