On the assumptions that Thomas's parents are James and Mary, that he was registered Thomas Wood, Dec Q 1899, Chapel en le Frith (7b 280), that he served in the theatre of war and that he survived: (a lot of assumptions, I realise

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The two most likely contenders from the MICs are; 200474 and 281501 (who also served with the Notts and Derbs Regt). 242679 was KIA.
Given his age, I would think it unlikely that he would have seen overseas service prior to 1917, the six figure service numbers generally coming into use in the spring of that year, even though he may have joined up earlier (drummer boy?).
The pensions records (WO364) only represent a small fraction of the service records. This link will explain it better than me:
http://www.nationalarchives.gov.uk/catalogue/RdLeaflet.asp?sLeafletID=18That's my best guess

Phil