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| OGF2704 Limited | Construction | 2025 |
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| OGH Solutions Limited | Real estate | 2018 |
| OGI Fibre Limited | Construction | 2021 |
| OGI Networks Limited | Information & communication | 1998 |
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| Oguntonovi Limited | Manufacturing | 2016 |
| Oguzhan Orcan Ltd | Wholesale & retail | 2025 |
| OH Agency Ltd | Professional & scientific | 2019 |
| OH Blimey Ltd | Professional & scientific | 2021 |
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| OHC Property 3 Limited | Construction | 2017 |
| OHC Property Five Limited | Construction | 2015 |
| OHC Property Four Limited | Construction | 2017 |
| OHC Property Limited | Real estate | 2017 |
| OHL Solar Ltd | Professional & scientific | 2021 |
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| OKC Construction Ltd | Construction | 2019 |
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| Okrug Premium PC | | 2020 |
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| Okto Creative Ltd | Professional & scientific | 2020 |
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| Okwheels Ltd | Wholesale & retail | 2016 |
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| Olcourse Ltd | Education | 2025 |
| Old Bailey Property Services Limited | Real estate | 2006 |
| Old Bill Media Limited | Information & communication | 2012 |
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| Old Court House Investments Limited | Real estate | 1999 |
| Old High Street Ltd | Administrative & support | 2018 |
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