Hi Peter,
I've been unable to find any pension records for William but the service records are only currently available online for the surnames A-N. O-Z will be available shortly so it's possible William's service records suvived the Blitz (I'm afraid we'll just have to wait). I have found his Medical Index Card (MIC) and here are the details:
Name: WILLIAM WATTERSON
Rank: Private
Regiment: 6th Bn South Lancashire Regiment
Regiment No: 12336
Medal entitlement: British Medal, Victory Medal Roll. J/1/103B4 Page.697. Star (1915) Medal Roll. J/1/1B2 Page.157
Theatre of war first entry: 2b Balkans (Gallipoli)
Date of first entry: 01/07/15
Date of Death: 09/04/1916
I'm not sure how much you've found out about William but because we know dates and his battalion we can piece quite a bit together. I hope the information I've found helps you in your quest:
South Lancashire Regiment details
6th (Service) Battalion
Formed at Warrington in August 1914 as part of K1 and moved to Tidworth, attached to 38th Brigade in 13th (Western) Division. Moved to billets in Winchester in January 1915 before going next month to Blackdown.
Sailed from Avonmouth in June 1915. Landed at Cape Helles (Gallipoli) 7-31 July then moved to Mudros. Landed at Anzac Beach 4 August 1915.
20 December 1915 : evacuated from Gallipoli and went to Egypt via Mudros.
February 1916 : moved to Mesopotamia.
13th Western Division Major engagements
Gallipoli
Battle of Sari Bair. 6-10 Aug 1915.
Russell's Top. 7 Aug 1915.
Hill 60. 21 Aug and 27-28 Aug 1915.
Evacuation of Suvla. 19-20 Dec 1915.
Last Turkish attack at Helles. 7 Jan 1916.
Evacuation of Helles. 7-8 Jan 1916.
Egypt
No major action (Garrison duty at the Suez canal)
Mesopotamia
Capture of Hanna and Fallahiya. 5 Apr 1916.
Second attack on Sannaiyat. 9 Apr 1916.
We can only image the horrors William witnessed at Gallipoli and Iraq sadly I've not continued after the attack on Sannaiyat 9th April 1916 because that was where he was sadly killed. The Division fought many other engagements in Iraq after Sannaiyat.
Interestingly the future Prime Minister Clement Atlee served with the 6th Battalion as a Captain during Gallipoli and Mesoptamian campaign and was wounded in the battle of El Hanna 5th April 1916 (maybe he was William's commanding officer). The national archive has information on Clement Atlee and shows an extract from the war diaries of the 6th Battalion 5th April 1916. If you wanted to look at the war diaries for the 6th Battalion you can download (£3.50 a piece):
Gallipoli, Dardenelles 11 Division, 38 Infantry Brigade, 6 Battalion South Lancashire Regiment. Includes appendices and map.. Part 9 of 32. Whole document available. November 1915 - December 1915
Gallipoli, Dardenelles 11 Division, 38 Infantry Brigade, 6 Battalion South Lancashire Regiment.. Part 8 of 32. Whole document available. September 1915 - October 1915
Gallipoli, Dardenelles 11 Division, 38 Infantry Brigade, 6 Battalion South Lancashire Regiment. Includes Appendices.. Part 7 of 32. Whole document available. July 1915 - August 1915
The war diaries for the Battalion in 1916 are only available at the Nation Archive in Kew but why not check the extract diary mentioned. I find the war diaries fantastic because they're written by serving officers detailing all actions and daily life of the Battalion.
Hope this helps any questions just ask.
Regards
Adrian
ps
Mudros was a small Greek port on the Mediterranean island of Lemnos. The Allies used Mudros to transport men and supplys to Gallipoli and evacuated the wounded from Gallipoli. The famous war poet Rupert Brookes died on April 23rd 1915 there. He fell ill and the medical staff attached to his unit diagnosed an infection caused by a mosquito bite. Also In late October 1918 the armistice between Turkey and the Allies was signed at Mudros. Mudros for such a small place is steeped in so much history.