Nesta
You have John Richard Jones, Railway Place getting married in Oct 1922. The list provides military info on John Richard Jones, 10 Railway Place. Newspaper articles show the name to the address. Ideally your cousin would clinch it by identifying No 10 from family lore or on a document?
The 6th Bn Royal Welsh Fusiliers published a list of its 1st line men (i.e 1st 6th Bn) that were killed/died of wounds/died/suffered disease & illness etc during the Gallipoli campaign up to 31st October 1915. The first three categories were also officially published in the 'national lists' in the Times and locally in local/regional papers but the disease/illness etc were not. The 6th Bn publication also provided a full address for most of those on it (the 'national' one did not) which makes it a handy list, given that many personal records were destroyed, in identifing men i.e military identity to name/address.
In terms of this particular query of yours all you gain from that list is what I have provided i.e Pte 1020 John Richard Jones, 10 Railway Place, Portmadoc suffered from dysentery. The list can be found in the RWF Archives now held at Wrexham County Archives and there is a copy at the library at Bangor Uni.
His personal papers do not seem to have survived but a pen picture of his war can be built up from material such as his medal card/rolls, casualty lists (he was wounded in 1917), newspaper clips etc and a working knowledge of RWF WW1. I will compile one if you wish.
Turning to the potential family in the 1901/1911. They do look a good fit don't they but I agree that you would want to be absolutely sure.
Accepting this is the family then the Robert Jones in the linked newspaper clip is a red herring. The 1911 shows they had 4 children and they are all named as Lewis, John Richard, William Arthur and Mary (last two same age- twins maybe, any family lore of that i.e your cousins parent had uncle/auntie who were twins?) No Robert. Looking at the clip where he is placed at no 10 I see that the list names John Richard Jones and William Jones at 10 Railway Place then William Jones 10 Church Street then Robert Jones, 10 Railway Place thus suggesting a typo i.e Railway instead of Church for Robert Jones.
Another bit of info that may jog memories/link into family lore:
Lewis Jones in the 1911 family is shown as a Grocer. Search for Lewis Jones and his year birth you'll also see a Lewis Jones same age, birthplace and occupation as a lodger at 25 Madoc Street, Portmadoc. It's not unheard of for someone to have more than one entry in the census.
The latter Lewis Jones looks to have military papers under his 265087 number. Brief summing up of his service is that he was a pre war Terittorial (6th Bn) enlisting as 815 in 1910. He went to Gallipoli and also suffered dysentery*** On recovery he has remained in the UK. Unfortunately his papers are not complete and don't give next of kin on enlistment etc. One form though does give a next of kin during wartime as wife, Lena Jones with an address of Queen(?) House, Church Stretton but a discharge address of The Stores, Portmadoc. I don't know whether this is 25 Madoc Street though or a different 'store'. They might be two different Lewis Jones i.e the 1991 Penmorfa one and the 1911 Portmadoc grocer but all the matching stuff is worth bringing to you attention plus your cousin might have familiy lore of an Uncle Lewis/Auntie Lena who ran a 'Store'.
[*** he is on that list but frustratingly at 3 Railway Place, the list does have some errors though. There is a Lewis Jones in the 1911 at No 12 but he is born 1877 and a Signal Fitter)
A structured search of the newspapers (esp wartime) using variants of the names and the addresses known might provide a further piece of you jigsaw. I find quite often that initials only are used for the christian names so 'J R Jones' etc are worth considering as search terms.
Lastly, I have just looked for a family tree on Ancestry. There are at least two for what appears to be the Penmorfa family that may be worth exploring with their authors (couple of discrepancies)
http://search.ancestry.co.uk/cgi-bin/sse.dll?db=pubmembertrees&gss=sfs28_ms_r_db&new=1&rank=1&MS_AdvCB=1&gsfn=john%20richard&gsfn_x=1&gsln=jones&gsln_x=1&msbdy=1895&msbdy_x=1&msbdp=1&gskw=port*&gskw_x=1&MSAV=2&uidh=a63
