Marcus,
I would agree with Frank. Pte Shurmer was awarded the QSA medal with WT, CC & TV clasps and the KSA medal with 1901 & 1902 clasps, which are actually the most common medal clasps for the Wiltshire's which shows that he was with the Regiment throughout the war. I have written a history of the 2nd Wilts which I hope to have published soon. I have checked everything I have and cannot identify his company at the moment. I will keep his name in mind and if anything else turns up I shall let you know. You should of course visit Kew and verify his record.
I cannot find anything about Hook, but the Yeomanry museum at Trowbridge might be able to help.
Ian