These are all the Issac Jones from the '51:
JONES, Isaac, s, u, 1, , BRE, Beaufort , 90/f238/p13
JONES, Isaac, sv, u, 17, tailor, MON Llangun, Tretower Shop, 90/f42/p13
JONES, Isaac, br, u, 19, iron miner, BRE Llanelly, Daren-felen, 90/f406/p7
JONES, Isaac, gs, u, 7, scholar, BRE Llanelly, Merthyr Road, 90/f363/p22
JONES, Isaac, h, m, 39, coal miner, BRE Llanelly, Waun Lapria, 90/f390/p40
JONES, Isaac, ld, u, 19, iron mine haulier, BRE Llanelly, Waun-y-bychan, 90/f452/p37
JONES, Isaac, s, , 11, coal haulier, BRE Llanelly, Cwm-nant-gam, 90/f436/p5
JONES, isaac, s, u, 1m, , BRE Brynmawr, Bailey Street, 90/f217/p27
JONES, Isaac, s, u, 21, blacksmith, BRE Llanelly, Pen-y-bont Cottage, 90/f634/p34
JONES, Isaac, s, u, 9, , BRE, Beaufort, 90/f257/p51
JONES Isaac, h, m, 67, farmer 258 acres+, BRE LF Abergwesyn, Maesllech, 88/f67/p9
JONES Isaac, h, m, 62, ag lab, BRE Llanwrtyd, Bwlch-bach, 70/f459/p1
JONES Isaac, h, m, 56, letter carrier+, BRE Llanwrtyd, Dderwenining 2, 70/f471/p12
JONES Isaac, h, m, 55, farmer 60 acres +, CMN Myddfai, Bryn-ddu, 89/f170/p14
JONES Isaac, h, m, 49, farmer 30 acres, BRE Llanigon, Upper Island, 91/f247/p6
JONES Isaac, h , m , 40, quarryman, BRE Defynnog, High Street, 59/ 733 093
JONES Isaac, h , m, 31, ironstone miner, BRE Llywel , Cefn, Lower, 59/714 159
JONES Isaac, h, m, 26, farmer emp with father, BRE LF Abergwesyn, Maesllech, 88/f67/p9
JONES Isaac, h, m, 25, farmer 100 acres, BRE LF Abergwesyn, Trallwn, 88/f15/p7
JONES Isaac, Lab, u, 27, ag lab, DEN Abergele, Tynywain, 89/f9/p10
JONES Isaac, s, u, 48, mason, BRE Llanafanfawr, Penywaun, 88/f97/p8
JONES Isaac, s , u, 17, coal miner, GLA Merthyr Tydfil,Cefn, Lower, 59/711 134
JONES Isaac, s , -, 15, mine haulier, BRE Cefncoedycymmer,Cefn, Lower, 59/710 127
JONES Isaac, s, u, 14, , BRE LF Abergwesyn, Llwyngwnfel, 88/f84/p4
JONES Isaac, s, , 11, emp at home, BRE Llanwrtyd, Caemawr, 88/f30/p12
JONES Isaac, s, , 11, scholar, BRE Brecon, Ship Street, 89/f466/p9
JONES Isaac, s, , 11, , BRE Glasbury, Tyndrain, 91/f269/p4
JONES Isaac, s , -, 9, labourer ironworks, BRE Penderyn, Big Row, 60/007 020
JONES Isaac, s, u, 7, , BRE Llanlleonfel, Garth Mill, 88/f66/p7
JONES Isaac, s , -, 4, -, CMN Llandovery, High Street, 59/ 760 155
JONES Isaac, s, u, 1, , BRE Llanlleonfel, Maesllech, 88/f67/p9
JONES Isaac, sv, u, 21, general servant, BRE Builth, Kings Head Inn, 88/f259/p8
JONES Isaac, sv, u, 18, farm lab, BRE Llangamarch, Gludy, 89/f378/p23
JONES Isaac, sv, u, 15, farm servant, BRE LF Abergwesyn, Llwynowen, 88/f13/p4
JONES Isaac , sv, , 12, farm servant, BRE Llanwrtyd, Penycae, 88/f20/p17
JONES Isaac?, s, u, 21, farm servant, BRE Llanwrtyd, Dderwenining 2, 70/f471/p12
JONES Isack, s , u , 16, coal miner, CMN Llangadog, Henglyn Isaf, 64\050 006
If any look likely let me know and I can give you the household. None will have an Alice of the right age with them though.
Kazza.