Lewis
You Should be able to get all your Guards Service records from the Guards archives at Birdcage Walk London as they were stored in a seperate place to the ones that were bombed in WW2
unfortunately i think it will cost you £30 for each record

The Coldstreamer is a pre war regular( i suspect about 1905 enlistment) ive researched a lad with a similar number.
I would check Ancestry first to see if any records are held on there if not apply to the individual Guards archives for their records.
Cracking set of stuff you have there there is the Princess Mary Christmas tin if you google it you will get something...may have belonged to your Coldstreamer as they were issued at Christmas 1914 and POWs were given them too.
Mustve been very sad for the Flavell family Two sons lost to the War.
Addendum
http://search.ancestry.co.uk/cgi-bin/sse.dll?gl=39&rank=1&new=1&so=3&MSAV=0&msT=1&gss=ms_f-39&gsfn=thomas&gsln=cunningham&gskw=6359+coldstream+guards&sbo=0&uidh=ip5£30 saved

Thomas Cunninghams pension records on ancestry
http://www.1914-1918.net/bat1.htmLooks like he was involved in the first battles of Great War and wounded in the thigh at Landrecies then became POW ( his war lasted 14 days! until capture at least he was a lucky one and survived)
4063 George Lunn enlisted Nov 1915 and discharged with sickness to pension in 1918
Cant see his record online so will be in Welsh Guards Archive.
Ady