Wikipedia is a good source for info re medals:
1939-1945 Star
The 1939–45 Star was a campaign medal of the British Commonwealth, awarded for service in the Second World War. The medal was awarded for operational service between 3 September 1939 and 2 September 1945.
• Army personnel had to complete 6 months service in an operational command. Airborne troops qualified if they had participated in any airborne operations and had completed 2 months service in a fully operational unit.
• Air Force personnel had to participate in operations against the enemy providing that 2 months service had been completed in an operational unit. Non-aircrew personnel had to complete 6 months service in an area of (overseas) operational army command.
• Naval personnel qualified if they completed 6 months service, and at least 1 voyage was made through an operational area.
• Royal Observer Corps personnel for service of 1080 days.
Africa Star
The Africa Star was a campaign medal of the British Commonwealth, awarded for service in the Second World War.
The Star was awarded for a minimum of one day service in an operational area of North Africa between 10 June 1940 and 12 May 1943. The whole of the area between the Suez Canal and the Strait of Gibraltar is included, together with Malta, Abyssinia, Kenya, the Sudan, both Somalilands and Eritrea. The areas not bordering the Mediterranean only qualified for the Africa Star from 10 June 1940 to 27 November 1941.
Italy Star
The Italy Star was a campaign medal of the British Commonwealth, awarded for service in World War II.
The medal was awarded for operational service (on land) in Italy, Greece, Yugoslavia, Pantelleria, the Aegean area and Dodecanese Islands, and Elba at any time between 11 June 1943 and 8 May 1945. Other areas to qualify for the award are:
• Sicily - between 11 June 1943 - 17 August 1943
• Sardinia - between 11 June 1943 - 19 September 1943
• Corsica - between 11 June 1943 - 4 October 1943
Atlantic Star
The Atlantic Star was a campaign medal of the British Commonwealth, awarded for service in World War II.
The star was awarded for six months service afloat, in the Atlantic or in Home Waters, within the period 3 September 1939 to 8 May 1945. Also awarded to aircrew who have taken part in operations against the enemy at sea within the qualifying areas for Naval personnel, subject to two months service in an operational unit. The 1939-1945 Star must have been earned before commencing qualifying service for the Atlantic Star.
War Medal 1939-1945
The War Medal 1939–1945 was a British decoration awarded to those who had served in the Armed Forces or Merchant Navy full-time for at least 28 days between 3 September 1939 and 2 September 1945. In the Merchant Navy, the 28 days must have been served at sea. It is sometimes described as the "Victory Medal" for World War II, although that is not its correct name.