Thanks Slowhands for all that. Tried the Phelps surname, not led me anywhere unfortunately. Don't think William had a second christian name.
The 1901 census in Factory Row I'm sure is the right family. He used the initial M after his and his wifes name, but after the daughter, who was born a base child with the surname Bennett he has used the initial B, Hilda B Phelps.
In the 1911 census she is Hilda Rose Ann Bennett age 12, living with the family in 18 Paget St, Ynysybwl, nr Pontypridd. The census shows that they had 9 children upto 1911, but only 6 were still living.

Thanks to all who have helped in this.