Hi Hilary,
in my limited experience searching for those who thankfully survived the horror of WW1 is actually harder than searching the fallen !. If you search "WW1" etc in the forum's search engine you'll find several threads on this subject, there are a perhaps surprising hign number of possible regiments that drew from the Forest. In fact it was only thro luck & persistence I eventually discovered the history of a Longhope ancestor of mine who was known to have died in the British Army in WW1 but no-one knew any more details at all, even the commemorative plaque they received from the War Office didnt say !. I trawled thro the records of War Graves sites (CWGC) assuming he was in the likes of the Herefordshire, Worcestershire, Glosters, Regiments etc to no avail. Eventually found the National Archives website which I think is best for you to try, apparently and to our great surprise our ancestor had actually joined the Royal Naval Volunteer Reserve which is essentially sailors converted to front line soldiers, not ships companies. I still dont know how or why this happened, but I do know quite a few Foresters joined them presumably after a particular recruiting drive ?.
I've seen photos of general recruiting rallies at various town centres around the area including my home town Cinderford, larger towns such as Chepstow & Monmouth would most definitely have them. Hence sadly theres a lot of possible Regiments for you to consider such as the Monmouthshires or even the Welsh Guards etc. Re Granville's trade, perhaps a shame he wasnt a collier, as he might well have joined one of the Tunnelling Batallions, search the forum for my posts on these. Possibly being a butcher might have dictated his eventual posting?

Anyhow best startpoint is the National Archives site, this caried records for WW1 particularly, there are almost 400 Biddles listed. Unfortunately they sometimes only give initials of first names but still very much worth a look. http://www.nationalarchives.gov.uk/documentsonline/search-results.asp?CatID=10&sear...

Everyone who fought received Campaign Medals so search these first, although as you say not all the records survived the bombing of London in WW2.

From this link I recommend you use the Advanced Search engine.

Like many search engines I recommend you dont try to be too specific with your search info. My ancestor is listed under Langhope instead of Longhope for example !.

Re the oddities of this search engine, just been using the "advanced search" engine looking thro the WW1 Campaign Medals section, tried searching for "Biddle, T" and it gives a different set of results for "Biddle, Thomas" for example !!.
So be carefull, methodical and patient !!
There are a few "Thomas W Biddle"s listed, wasnt a Gunner by any chance ?.

I discovered this site via my local library's free (but SLOW!) Ancestry pc, which may be a quicker method if you prefer.

Hope this helps, I'll try and post more later.

ps presumably this is your Granville,

Record_ID: 68837
Entry_Number: 373
Year: 1898
Month: Oct
Day: 19
Parents_Surname: BIDDLE
Child_Forenames: Granville Harry
Fathers_Forenames: Harry
Mothers_Forenames: Minnie Mary
Mothers_Surname:
Residence: Alvington
Occupation: Farmer
Officiating_Minister: William Somerset Rector
Event: Baptism
Memoranda:
Notes:
Register_Reference: P376 IN 1/11
Page_Number: 47
Parish_Chapel: Woolaston
Soundex: B340

One of my ancestors actually got married during WW1, perhaps because of this his Marriage Record quoted his rank and regiment which was news to us. Perhaps this is so with one of your relatives ?.
This Longhope lad was actually in the Monmouthshire Infantry Regiment (so no logical family or geographical ties to Wales but still !??) which thankfully has a website listing many of the members, including him. Sadly no Biddles are listed.
http://www.1stbattmons.co.uk/10.html
There is also a good website for the Monmouthshire Engineers Militia, sadly again I cannot find Biddles listed there.
http://www.monmouthcastlemuseum-archives.org.uk/regsearch.php?func=listsurnames

The search continues.... but a look on Ancestry etc may well be quickest if you have access to it (I don't except via the Library, have you tried yours ?).

1911 census

Signature: Minnie BIDDLE
St Arrans
Chepstow
Monmouthshire

Living in 8 rooms

Harry BIDDLE - 43 - married 22 years, six children born alive and none have died
Farmer, on the Farm, Employer, born Tidenham, Glos

Minnie BIDDLE - 36, Farmer's Dairy, born Tytherington Glos

Robert BIDDLE - son, 18 - Single, Farmer's Son, born Woolaston, Glos

Frederick BIDDLE - son - 16 - born Woolaston

Thomas BIDDLE - son - 14 - born Alvington

Harry BIDDLE - son - 12 - School, born Alvington

John BIDDLE - 6 - School, born Chaple Hill

Charlie BIDDLE - Nephew - 14 - Visitor, born Woolaston

Thomas EDWARDS, Servant, 55 - General Labourer, on the Farm, Worker, born Alvington

Hannah HEYDEN - Servant, 55, Domestic Servant - on the Farm, Worker, born Trellick

-----

Looking at Military Records on Ancestry

so far can see

Clement BIDDLE's records (19 images) - age 26 years and two months
Myrtle Cottage
Penprisk
Rencoed
Bridgend

dated 11 December 1915

Royal Field Artillery : Reg.No. 258508

Married to Gertrude Ellen Biddle - born in 1889

FreeBDM : Clement L.C. Biddle married Gertrude BROWN - Chepstow District 1913

--

1911 Census, Hanley, Tidenham, Chepstow

Mosa E JOYCE - 44 - Widow, Farmer, born Alveston, Gloucestrshire
Francis W JOYCE - son - single, born Tidenham, Glos
Alfred H JOYCE - son - 13 - born Tidenham Glos
Frederick L JOYCE - son - 9 - born Tidenham
Clement L C BIDDLE - Visitor, 21, Single, Farm bailiff - born Woolaston, Glos
Fanny TERRELL, Servant, 16 - single, Domestic Servant, born Alvington, Glos