| # | Tower | No | Year | Materials | Maker | Trusses | Layout |
|---|
| 6501 | Old Fletton, Cambridgeshire, S Margaret | 1 | 1953 | Cast iron | John Taylor & Co | 8.3.A.h | 4.3 |
| 6502 | Old Hill, West Midlands, Holy Trinity | 1 | 1947 | Cast iron | Gillett & Johnston | 8.3.A.m | 8.3 |
| 6503 | Old Leake, Lincolnshire, S Mary | 1 | 1671 | Timber | | 6.B | |
| 6504 | Old Malton, North Yorkshire, S Mary V | 1 | c1880 | Timber | Local labour/guild/assn | 5.A | 3.1 |
| 6505 | Old Milverton, Warwickshire, S James | 1 | c1880 | Timber | | | |
| 6506 | Old Newton, Suffolk, S Mary | 1 | 1896 | Oak | Alfred Bowell | 6.A | 6.4 |
| 6507 | Old Radnor, Powys, Wales, S Stephen | 1 | c1799 | Oak | | | |
| 6508 | Old Swinford, West Midlands, S Mary | 2 | 1959 | Cast iron | John Taylor & Co | | |
| 6509 | Old Swinford, West Midlands, S Mary | 1 | 1959 | Cast iron | John Taylor & Co | | |
| 6510 | Old Warden, Bedfordshire, S Leonard | 1 | 1899 | Cast iron | John Taylor & Co | 8.3.C.e | 6.4 |
| 6511 | Old Weston, Cambridgeshire, S Swithun | 1 | c1699 | Oak | | 6.B | 4.3 |
| 6512 | Old Whittington, Derbyshire, S Bartholomew | 1 | | Timber | | | 6 |
| 6513 | Old Windsor, Berkshire, S Peter & S Andrew | 1 | 1890 | Oak | Mears & Stainbank | | |
| 6514 | Old Wolverton, Buckinghamshire, Holy Trinity | 1 | c1820 | Timber | | 6.B & 6.D | 6.X |
| 6515 | Oldberrow, Warwickshire, S Mary | 2 | 1875 | Timber | ? (unidentified) | | |
| 6516 | Oldberrow, Warwickshire, S Mary | 1 | 1875 | Timber | ? (unidentified) | | |
| 6517 | Oldbury, West Midlands, Christ Church | 2 | 1887 | Timber | John Warner & Sons | 6.S | 4.3 |
| 6518 | Oldbury, West Midlands, Christ Church | 1 | 1887 | Timber | John Warner & Sons | 6.S | 4.3 |
| 6519 | Oldham, Greater Manchester, S Mary | 3 | 1922 | Cast iron | John Taylor & Co | 8.3.A.h | 4.5 ➔ 5.X |
| 6520 | Oldham, Greater Manchester, S Mary | 3.1 | 1983 | Cast iron | John Taylor & Co (Bellfounders) Ltd | 8.3.A.h | 1 |
| 6521 | Oldham, Greater Manchester, S Mary | 2 | 1922 | Cast iron | John Taylor & Co | 8.3.C.e | 5.1 |
| 6522 | Oldham, Greater Manchester, S Mary | 1 | 1922 | Cast iron | John Taylor & Co | 8.3.C.e | 3.3 |
| 6523 | Oldland, Gloucestershire, S Anne | 1 | | Stone | | 9.A | 1 |
| 6524 | Ollerton, Nottinghamshire, S Giles | 1 | | Timber | | 6.B | 1 |
| 6525 | Olney, Buckinghamshire, S Peter & S Paul | 1 | 2009 | Cast iron | Whites of Appleton | | |
| 6526 | Olveston, Gloucestershire, S Mary V | 1 | 1907 | Composite | John Sully | 7.A.a ? | 8.3 |
| 6527 | Ombersley, Worcestershire, S Andrew | 1 | 1828 | Timber | ? Jacques family | 6.A & 6.I | 6.X |
| 6528 | Onibury, Shropshire, S Michael & All Angels | 1 | 1626 | Timber | | 6.A | 4.1 |
| 6529 | Orange, New South Wales, Australia, Holy Trinity | 1 | 2005 | Steel | Ron Shepherd | 8.1.B.a | 8.3 |
| 6530 | Orby, Lincolnshire, All Saints | 1 | 1921 | Steel | Mears & Stainbank | | |
| 6531 | Orchard Portman, Somerset, S Michael | 1 | 1746 | Oak | William Duck | | |
| 6532 | Orcheston, Wiltshire, S Mary | 1 | | Timber | | | |
| 6533 | Orcop, Herefordshire, S John Bapt | 1 | 1907 | Oak | William Greenleaf | 6.A | 5.X |
| 6534 | Ordsall, Nottinghamshire, All Hallows | 2 | 1892 | Cast iron | John Taylor & Co | | |
| 6535 | Ordsall, Nottinghamshire, All Hallows | 1 | 1892 | Cast iron | John Taylor & Co | 8.3.C.e | 5.4 |
| 6536 | Orford, Suffolk, S Bartholomew | 2 | 1915 | Timber | George Day & Sons | 6.D | 2.X1 |
| 6537 | Orford, Suffolk, S Bartholomew | 1 | 1998 | Cast iron & steel | Eayre & Smith | 8.2.A.b | 8.3 |
| 6538 | Orleans, Massachusetts, United States of America, The Transfiguration | 1 | 2009 | Steel | Whitechapel Bell Foundry | 8.1.B.c | 10.4 |
| 6539 | Orleton, Herefordshire, S George | 1 | | Oak | | | 4 |
| 6540 | Orlingbury, Northamptonshire, S Mary | 1 | c1843 | Oak | Local labour/guild/assn | 6.A | 4.X ➔ ~ 6.5 |
| 6541 | Orlingbury, Northamptonshire, S Mary | 1.1 | 1993 | Cast iron | John Taylor & Co | 8.3.A.h | 2.X1 |
| 6542 | Ormesby, North Yorkshire, S Cuthbert | 2 | 1908 | Cast iron | John Taylor & Co | 8.3.D.a | 4.2 |
| 6543 | Ormesby, North Yorkshire, S Cuthbert | 1 | 1908 | Cast iron | John Taylor & Co | 8.3.D.a | 4.2 |
| 6544 | Ormskirk, Lancashire, S Peter & S Paul | 8 | | | | | |
| 6545 | Ormskirk, Lancashire, S Peter & S Paul | 1 | | Oak | | 6.A | 8.3 |
| 6546 | Orsett, Essex, S Giles & All Saints | 1 | 1791 | Oak | | 6.A | 6.1 |
| 6547 | Orston, Nottinghamshire, S Mary | 1 | 1923 | Cast iron | Gillett & Johnston | | |
| 6548 | Orton Waterville, Cambridgeshire, S Mary | 1 | <1709 | Oak | | 6.A | 4.3 |
| 6549 | Orwell, Cambridgeshire, S Andrew | 1 | 1931 | Cast iron | John Taylor & Co | | 6 |
| 6550 | Osbournby, Lincolnshire, S Peter & S Paul | 1 | | Timber | | | 3 D |