| Castell 2022-1 PLC | London | 2022 |
| Castell 2023-1 Holdings Limited | London | 2023 |
| Castell 2023-1 PLC | London | 2023 |
| Castell 2023-2 Holdings Limited | London | 2023 |
| Castell 2023-2 PLC | London | 2023 |
| Castell 2025-1 Holdings Limited | London | 2025 |
| Castell 2025-1 PLC | London | 2025 |
| Castell 2026-1 Holdings Limited | London | 2025 |
| Castell 2026-1 PLC | London | 2025 |
| Castell Coch Investments Limited | Stonehouse | 2015 |
| Castell CYF | Cardiff | 1997 |
| Castell Investments Limited | Norwich | 2006 |
| Castellain Associates Limited | London | 2021 |
| Castellarius Ltd | Manchester | 2024 |
| Castello Ventures Limited | London | 2011 |
| Castellum Trustee Limited | Stonehouse | 2026 |
| Castelnau Capital Partners Limited | Southend-On-Sea | 2018 |
| Castelnau Limited | London | 2018 |
| Castelnau Medina Limited | London | 2022 |
| Castelynn Capital Ltd | Hornchurch | 2026 |
| Casterbridge Holdings Limited | Bournemouth | 2016 |
| Casterbridge Wealth Limited | Salisbury | 2015 |
| Castfeld Estates Holdco Limited | London | 2025 |
| Castiga Investments Ltd | Doncaster | 2024 |
| Castil Ltd | Wollaston | 2021 |
| Castile Acquisitions Ltd | London | 2016 |
| Castill | Eastleigh | 2014 |
| Castille Capital Global Markets Ltd. | London | 2018 |
| Castillo Blanco Ltd | Uxbridge | 2019 |
| Castillo Holdco Limited | Loughton | 2020 |
| Castillo Investments Ltd | Droitwich | 2019 |
| Castillon Advisory Ltd | London | 2025 |
| Castings Technology Holdings Limited | Rotherham | 2020 |
| Castior Limited | Bath | 2010 |
| Castle (Frimley) Ltd | Ilford | 2020 |
| Castle (Kingswinford) Holdings Ltd | Brierley Hill | 2018 |
| Castle 45 Holdings Limited | Berkhamsted | 2024 |
| Castle Acquisition Limited | London | 2019 |
| Castle Actuarial Ltd | Salford | 2020 |
| Castle Agencies Ltd | Dartford | 2013 |
| Castle Aviation Limited | Rochdale | 2025 |
| Castle Bidco Home Loans Limited | Addlestone | 2021 |
| Castle Building Contractors (Holdings) Limited | Bury St. Edmunds | 2020 |
| Castle Business Finance Ltd | London | 2016 |
| Castle Capital Holdings Ltd | London | 2021 |
| Castle Capital Limited | Banbridge | 2022 |
| Castle Cartons (2011) Limited | Birmingham | 2011 |
| Castle Cement (Ketton) Limited | Maidenhead | 1928 |
| Castle Cement (Ribblesdale) Limited | Maidenhead | 1935 |
| Castle Coachworks (Northampton) Holdings Limited | Northampton | 2025 |
| Castle Coatings (Holdings) Limited | Caerphilly | 2019 |
| Castle Commercial Limited | Birmingham | 2018 |
| Castle Corporate Finance Limited | London | 2007 |
| Castle Corporate Investments Ltd | London | 2021 |
| Castle Decor (Holdings) Limited | Glasgow | 2020 |
| Castle Donnington Limited | London | 2017 |
| Castle Eden Properties Ltd | Gosport | 2014 |
| Castle Enigan Farms Limited | Newry | 2025 |
| Castle Estates (Nottingham) Holdings Limited | Nottingham | 2026 |
| Castle Estates Yorkshire Ltd | Sowerby Bridge | 1992 |
| Castle Finance (Essex) Limited | Colchester | 2021 |
| Castle Financial Consultants Limited | Falkirk | 2016 |
| Castle Financial Planning Ltd | | 2008 |
| Castle Financial Services (South East) Limited | Maidstone | 2006 |
| Castle Financial Services Ltd | Dursley | 2002 |
| Castle Financial Solutions Ltd | Nottingham | 2011 |
| Castle Gant Limited | Wallasey | 2008 |
| Castle Glen Development Company Limited | Belfast | 1997 |
| Castle Green Associates Limited | Nr Aldershot | 2004 |
| Castle Harbour Investments Limited | London | 2014 |
| Castle Hill Finance Ltd | Westcliff-On-Sea | 2024 |
| Castle Holding Group Ltd | Rugeley | 2009 |
| Castle Holdings (North East) Limited | Middlesbrough | 2026 |
| Castle Holdings Investment Limited | Derby | 2022 |
| Castle Homes Holdings Limited | Shrewsbury | 2018 |
| Castle Horizon Ltd | Worthing | 2025 |
| Castle Hotel (Subco) Limited | St Austell | 2020 |
| Castle House (Holdings) Ltd | Manchester | 2025 |
| Castle House Care (Holdings) Limited | Torquay | 2011 |
| Castle Housing Limited | Cheltenham | 2002 |
| Castle Hume Court | Enniskillen | 2018 |
| Castle Industrial Supplies Holdings Ltd | Carnforth | 2020 |
| Castle Insurance Services (North East) Ltd | London | 2009 |
| Castle Intermediate Holding II Limited | London | 2019 |
| Castle Intermediate Holding III Limited | London | 2019 |
| Castle Intermediate Holding IV Limited | London | 2019 |
| Castle Intermediate Holding Limited | London | 2019 |
| Castle Intermediate Holding V Limited | London | 2019 |
| Castle Investment Holdings Limited | London | 2026 |
| Castle Investment Solutions Ltd | Falmouth | 2010 |
| Castle Investments Holdings Ltd | Carnforth | 2026 |
| Castle KC Limited | Taunton | 2022 |
| Castle Keep Financial Solutions Limited | Newcastle Upon Tyne | 2018 |
| Castle Keep Holdings Limited | Malvern | 2017 |
| Castle Kelly Holdings Limited | Stanmore | 2023 |
| Castle Lane Consulting Limited | Stoughton | 2019 |
| Castle Loans Ltd | Bristol | 2013 |
| Castle Loch Ltd. | Carnforth | 2023 |
| Castle MC Holdings Ltd | Newtownards | 2019 |
| Castle Mews Holdings Ltd | Wrexham Industrial Estate | 2025 |