Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 23. Location of Military Objectives outside Densely Populated Areas
The UK LOAC Pamphlet (1981) provides: “The belligerents should endeavour to avoid siting their military installations near the civilian population.” 
United Kingdom, The Law of Armed Conflict, D/DAT/13/35/66, Army Code 71130 (Revised 1981), Ministry of Defence, prepared under the Direction of The Chief of the General Staff, 1981, Section 4, p. 14, § 4(d).
The UK LOAC Manual (2004) states: “Parties to a conflict are required, to the maximum extent feasible, to … avoid locating military objectives within or near densely populated areas.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.36.
In reply to a question in the House of Lords with respect to the 1991 Gulf War, a UK government spokesman stated:
The noble Lord asked if the bombing of civilians was not contrary to the Geneva Convention. The answer to that is no. We attacked targets accepted as legitimate in international law. Iraq’s stationing of military targets in civilian areas was contrary to the rules of war. 
United Kingdom, House of Lords, Statement by a government spokesman, 6 March 1991, Hansard, Vol. 526, col. 1485.