Lotsa.org.uk
Lists the age restrictions for different products in the UK, as well as acceptable forms of identification.
http://www.lotsa.org.uk/Printfriendly/pf_bus_age_restricted_sales.htm

Surrey County Council
Gives details of age restricted products in the UK such as alcohol.
http://www.surreycc.gov.uk/sccwebsite/sccwspages.nsf/LookupWebPagesBy
TITLE_RTF/What+age+restrictions+are+there+on+productsQ?opendocument

Young Wrexham
British age laws detailed.
http://www.youngwrexham.co.uk/rights/at_what_age.htm