Cant comment on their credentials but had experience with them on my last company. We switched form them to LRQA and the difference was that LRQA audited very in depth.

In the oil & gas industry, a lot of companies will not make it onto an AVL unless the registration body is UKAS accredited. I haven't got first hand experience of receiving a certification audit from QMS but i have heard from some companies that it isn't much more than a document review and lacks any real depth to make it a worthwhile audit. They are happy to take your money and give you a certificate but ultimately, without the UKAS logo, it lacks credability. I would stay clear and use one of the establised certification bodies such DNV, LRQA, NQA, API, Moodys, BV etc. This will have much more value for your organization.

I've never used QMS for 18001 but I came across them when I was back on the "dark side" working as a quality manager. Anyone can issue any certification against any standard system - it's only when you claim to have some authority to do so (such as UKAS) that you don't that you can run into trouble! In fact many companies are "self certifying" against 9001, 14001 and 18001. I seem to remember that back in those days one of the unapproved cert bodies (may not have been QMS) got into trouble with Trading Standards for selling their certifications as having more value than they did, but I can't really remember. You would think that the "guaranteed pass" nature of their system would make any thinking person question the worth of the certifications they're offering, but from the number of vehicles I see driving around with their logo (and that of other unapproved bodies), it seems they're getting lots of business. As someone before me said, we used LRQA when I was a QM for 9001 and found them excellent, and I'll certainly recommend them for 18001 when we go for formal certification.