Hi Ike,
On the lab reports in question, they state that some of the tests are "not included in the UKAS Accreditation Schedule for the Laboratory". As I understand it, there is no specific ISO standard for identification and quantification of these particular compounds, therefore, it can't be listed as one of the specific tests on their (or anyone elses) Accreditation Schedule. This is not unusual and I am sure there's a lot of other analysis this lab and other accredited labs perform that isn't specifically documentated in their Schedules, and this is precisely why one should require labs performing these tests to be accredited to a particular standard. This lab is accredited by UKAS to ISO/IEC 17025:2005 which is an internationally recognised standard, within which some labs (including this one) have a flexible scope which covers the specification and provision of other testing activities that don't directly appear in the schedule. Their ongoing accreditation is continuously monitored, both within the detailed scope of their Accreditation Schedule, and without, so that official bodies, government departments, the courts, small businesses and individual consumers can trust that the methodologies they design and use, product accurate and repeatable results.
Document LAB39 from the UKAS library states in section 2.2:
2.2 Flexible scopes of accreditation can allow a laboratory to undertake certain tests/calibrations, and to report the results as accredited, even though they may not be explicitly stated on their accreditation schedule.
This may involve:
(a) the inclusion of new or amended tests in accordance with a generic method;
(b) the modification of existing methods to broaden their applicability (e.g. to deal with new materials tested or properties measured, etc);
(c) the inclusion of newly revised or technically equivalent standard methods that are already covered by accreditation.
It's a very complex area with lots of ongoing documentation and monitoring, and I am sure if you contacted the lab yourself, they'd be happy to explain some of the hoops they must go through in order to maintain their accreditation.
Incidentally, I believe Enthalpy in the US also hold ISO17025:2005 accreditation.