United Kingdom of Great Britain and Northern Ireland (Includes England, Scotland, Wales, Northern Ireland) (KD - Eng & Wales; KDC - Scotland; KDE - No. Ireland)

Lii: 

BaiLII;
WorldLII
;
CommonLII; CommonLII (Pitcairn Islands)

Online Guides: 

LLRX; LLRX (constitution); LLRX (primary legislation); GlobaLex; GlobaLex (micro-states); GlobaLex (Scotland); GlobaLex (Ireland); GlobaLex (Wales); LOC

Gazettes: 
Other Database(s): 

Justis (laws, cases up to 1875&statutory documents - Yale network only)

JustCite (A neutral multi-source electronic citator for UK and EU (and ECHR) material, including cases, statutes, legislation, treaties, scholarly articles, and more; it links your search to case law, legislation and articles from numerous third-party publishers, and shows how they relate to each other)

ICLR Online Library (Publications of the Incorporated Council of Law Reporting (ICLR) for England and Wales. In addiition to the official Law Reports, ICLR publishes the Weekly Law Reports, the Industrial Cases Reports, the Business Law Reports, the Public and Third Sector Law Reports, and the Consolidated Index to leading law reports)

UK Parliament (publications)

British and Irish Legal Institute (public legal information)

Northern Ireland Case Database

Scottish Courts (case law database)

Lexis (Treaties & International Agreements, Case Law, Legislation & Regulations, Journals, Law Lists & Directories, Legal Updates, Lexis-Nexis Practice Materials, Commentaries & Treatises, International Arbitration, Mealey Publications

Westlaw (Case Law, Legislation, Statutes, All Reports, Law in Force, Legal & Regulatory Developments Index - LRDI)

N-Lex