Hi again, 
The best I can see is this very confusing entry:
RG10/5332 42 20 
Trevethin Southill
Tranch   
Margaret Forest, head, mar, 35, b. Ireland
John, son, 10, scholar, b. do. 
Patrick, son, 8, scholar, b. do. 
William, son, 1, b. Mon Panterg (?)
Bridget Field, stepmother, wid, 54, b. Ireland  William Field, son, unm, 28, Miner, b. do. 
Sarah Field, dau, 4, b. Mon Tranch  
The reference you quote has me confused as well.... HO107 is either 1841 or 1851  

Not sure this helps much... 
Tanja  
