We do not recommend any particular instruments or manufacturers, however, you may like to look at the following web sites:
Enertech Consultants
http://www.enertech.net/
Makers of the "Emdex" range of meters (see photo)
Perspective Scientific: http://www.perspective.co.uk/
(May 2010: Perspective's website no longer seems to be available)
Holaday Industries
we cannot currently locate Holaday's website
Among other meters, make a single axis combined electric and magnetic field meter (see photo)
Narda (formerly Wandel and Goltermann)
http://www.narda-sts.us/products_lowfreq_meters.php
Among other meters, make a three-axis electric field meter (see photo)
Instrument suppliers
EMFields: http://www.emfields.org/
EMFUK: http://www.emfuk.co.uk/
Enertech meters are available directly from the manufacturer
TICS: http://www.tics.co.uk/testequipment/w&g_acterna/index.html
TomsGadgets: http://www.tomsgadgets.com/products/categories.aspx?cat1=5
(we will be happy to list other vendors of these instruments if we are made aware of them)
Measurement services
Again, we do not recommend any particular organisation, but we are aware of the following who provide measurement services:
Electromagnetic Surveys Ltd: http://www.em-surveys.co.uk/
Cobham Technical Services: www.cobham.com/technicalservices