It is the British Army and regiments, it is NEVER easy
!!!
Firstly, the problem. There are many different Yorkshire and Lancashire regiments, each comprised of several battalions (sometimes 40 to 50) which served independently of each other in different divisions and brigades. They had different origins, eg regular pre-war army and their reserves, Territorial Force (part time militia), New Army (Kitchener's volunteers) which tended to group which brigades and division they served under. However, while the (fairly standard) uniforms and cap badges were standard to the regiment, the insignia and battle badges worn related to the brigades and divisions they served under, which could change in the course of the war, so the 35 battalions of the The Prince of Wales Own (West Yorkshire) Regiment served in about 12 different divisions.
Now part of the the answer is a great website called The Long, Long Trail, The British Army in the Great War of 1914-18:
http://www.1914-1918.net/army.htmWhich will allow you to track where any one regiment's battalions served and which battalions served in any given brigade or division. However, you now need to track what badge any battalion would have worn on a given date, and I am afraid I don't know of an online resource for that. However, I would start, with Mike Chappell's
http://www.amazon.co.uk/British-Battle-Insignia-1914-18-Men-at-arms/dp/0850457270/ref=pd_sim_b_2?ie=UTF8&refRID=1E5APE5KT6H6S7XNCTBS