The Home Office Drug Strategy Unit (DSU) is the licensing and regulatory body for precursor chemical control within the UK.  If you require a license or advice on obtaining a licence to comply with drug precursor chemical regulations you will need to contact their Drugs Licensing section. 

The Home Office Drug Strategy Unit can be contacted at:

Drug Licensing (Precursor Chemicals)
Drug Strategy Unit
Peel Building
2 Marsham Street
London
SW1P 4DF
Telephone: +44 (0) 207 035 0480

For general information: homeoffice.gov.uk

SOCA is the competent authority for the purposes of receiving notifications from industry on unusual orders or transactions involving scheduled substances. Such notifications should be made on the SOCA preferred form known as a Chemical Suspicious Activity Report (CSAR) Form, available from the Download the CSAR Form.