Thanks Cas.
I'm pretty certain it must have been a mistake by the registrar & the address was, as you say, 32 Gwernifor St.
Up until recently I was a member of ancestry.co.uk. I managed to construct my tree with about 1100 family members but my maternal Welsh great grandmother & her son remain a bit of a mystery. Her name, which I only just had confirmed 100% was Mary Ann Jones & her son (my maternal grandfather) was Edward Jones b. 28/12/08. The birth was registered in the sub-district Llantrisant in January 1909, the birthplace being down as Pontypridd.
We do not know who his father was, but I managed to place my 2 year old illegitimate grandfather Edward Jones as an inmate at Llantrisant workhouse in the 1911 census. This matches the birth certificate.
Unfortunately the birth certificate which I scanned part of in my original post only came through recently & I did not get to do a partial search for Mary Ann Jones at 32 ........ , Mountain Ash in the 1901/11 census.
I'll probably bite the bullet & join for another month, but I'm waiting on Edward's marriage certificate to come through, which may shed a little more light.
Thanks anyway.