| 1INSTALL Group Ltd | London | 2016 |
| 1K1 Security Services Ltd | Potters Bar | 2017 |
| 1LEGACY Limited | London | 2021 |
| 1LIFE Holdco Limited | Chorley | 2023 |
| 1LINEHIRE Ltd | Slough | 2025 |
| 1LOD Ltd | London | 2017 |
| 1LWW Co Limited | Nottingham | 2022 |
| 1M Concierge Limited | Warwick | 2025 |
| 1M1 Group Limited | London | 2022 |
| 1MPACT Solutions Ltd | Birmingham | 2024 |
| 1NESS Global Partners (UK) Limited | London | 2025 |
| 1NTRA Ltd | London | 2020 |
| 1NVER Limited | London | 2024 |
| 1OF1 Marketing Limited | Slough | 2025 |
| 1ON1 Limited | Ilford | 2018 |
| 1PGR Services Ltd | Wokingham | 2014 |
| 1PLUS Rental Ltd | London | 2019 |
| 1RG Investments Limited | Colindale | 2020 |
| 1SA Recruitment Limited | Birmingham | 2024 |
| 1SC Guarding Limited | London | 1997 |
| 1SEVEN Solutions Limited | Bedford | 2012 |
| 1SHARPE Loans UK Limited | Sheffield | 2025 |
| 1SOVEREIGN Ltd | London | 2008 |
| 1SRLEASING Ltd | London | 2021 |
| 1ST & 1ST Ltd | Leicester | 2020 |
| 1ST 4 Carpet Cleaning Ltd | Rayleigh | 2014 |
| 1ST 4 Cleaning Supplies Limited | St Albans | 2010 |
| 1ST 4 Repairs Ltd | Kent | 2005 |
| 1ST 4 Safety Ltd | Waterlooville | 2022 |
| 1ST 4 Stamps Limited | Nottinghamshire | 2007 |
| 1ST 4 Thirst Ltd | Iver | 2004 |
| 1ST A.C.E. Security Limited | Bromley | 2002 |
| 1ST Ace Fire Dynamics Limited | Bromley | 2004 |
| 1ST Ace Response & Guarding Ltd | Bromley | 2010 |
| 1ST Active Security Ltd. | Glasgow | 1997 |
| 1ST Advanced Landscapes Limited | Hindhead | 2022 |
| 1ST AID 4 Fencing Ltd | Somerset, Bath | 2022 |
| 1ST AID Gutter Vacume Service Ltd | London | 2026 |
| 1ST AID Training (North West) Ltd | Bamford, Rochdale | 2009 |
| 1ST Airport Link Ltd | Waterlooville | 2012 |
| 1ST Alarm Security Limited | Stockport | 2013 |
| 1ST Alert Alarm Systems Ltd | Co Tyrone | 2006 |
| 1ST Alternative Medical Staffing Ltd | London | 2009 |
| 1ST and 2ND FIX Ltd | Sutton Coldfield | 2018 |
| 1ST Approach Taxi Hire Ltd | Birmingham | 2024 |
| 1ST Armour Security Limited | Weston Super Mare | 2018 |
| 1ST Attendance Limited | Exeter | 1999 |
| 1ST Attendance Training Group Ltd | Bristol | 2022 |
| 1ST Base Machinery Sales Limited | Warrington | 2009 |
| 1ST Call Agency Limited | Rye | 2020 |
| 1ST Call Business Services Limited | Manchester | 2019 |
| 1ST Call Car Hire Ltd | Bolton | 2020 |
| 1ST Call Care 247 Ltd | Rainham | 2026 |
| 1ST Call Cleaning Services Limited | Ashford | 2026 |
| 1ST Call Damp Specialist Ltd | Friskney | 2011 |
| 1ST Call Drainage Solutions Ltd | 915 High Road | 2017 |
| 1ST Call Healthcare Ltd | Heckmondwike | 2010 |
| 1ST Call Lock and Key Shop Ltd | Bromsgrove | 2014 |
| 1ST Call Maintenance Limited | Kenilworth | 2017 |
| 1ST Call Plant Hire Ltd | Gloucester | 2020 |
| 1ST Call Plant Limited | Gloucester | 2017 |
| 1ST Call Recruitment (Lincoln) Limited | Chesterfield | 2018 |
| 1ST Call Recruitment Services Ltd | Chorley | 2018 |
| 1ST Call Storage Limited | Stonehouse | 2014 |
| 1ST Call Stroud Limited | Stonehouse | 2010 |
| 1ST Call Unique Drives and Paving Ltd | Luton | 2012 |
| 1ST Call Window Cleaning Bromley Limited | Westerham | 2026 |
| 1ST Call Window Cleaning Ltd | Ashford | 2018 |
| 1ST Car Imports Limited | Rickmansworth | 2008 |
| 1ST Care & Recruitment Services Ltd | Belfast | 2026 |
| 1ST Care Hygiene Ltd | Grimsby | 2009 |
| 1ST Centurion Security Services Limited | London | 2024 |
| 1ST Choice 4 Cleaning Ltd | Leicester | 2019 |
| 1ST Choice Accounting Services Limited | London | 2017 |
| 1ST Choice Alarms Ltd | Blackburn | 2006 |
| 1ST Choice Care Limited | Nottingham | 2025 |
| 1ST Choice Computer and Management Appointments Limited | Ashford | 1988 |
| 1ST Choice Consultants Ltd | Ruislip | 2024 |
| 1ST Choice Drains Limited | Bridlington | 2003 |
| 1ST Choice Fire and Flood Restoration Ltd | Paisley | 2020 |
| 1ST Choice GAS Services Limited | Bucks | 2000 |
| 1ST Choice Healthcare Recruitment Ltd | St. Albans | 2015 |
| 1ST Choice High Level Cleaning & Maintenance Limited | Portsmouth | 2003 |
| 1ST Choice Hire Van & Car Ltd | Sheffield | 2017 |
| 1ST Choice Inflatables Limited | Gillingham | 2005 |
| 1ST Choice Landscaping & Building Services Ltd | Doncaster | 2021 |
| 1ST Choice Landscaping & Paving Ltd | Erith | 2025 |
| 1ST Choice Landscaping & Tree Services Ltd | Cross Keys | 2023 |
| 1ST Choice Leisure Ltd | Birmingham | 2012 |
| 1ST Choice PA Ltd | Rugby | 2019 |
| 1ST Choice Payroll Limited | Ripon | 2003 |
| 1ST Choice Plant and Tool Hire Ltd | London | 2021 |
| 1ST Choice Plant Hire & Construction Ltd | Wigan | 2021 |
| 1ST Choice Protekta Limited | London | 2023 |
| 1ST Choice Security Gate Systems Limited | Bedford | 2022 |
| 1ST Choice Security Systems Ltd | Bedford | 2005 |
| 1ST Choice Staff Recruitment Limited | Chester | 2012 |
| 1ST Choice Staffing Ltd | Wembley | 2025 |
| 1ST Choice Support Ltd | Bradford | 2022 |
| 1ST Choice Tool & Plant Hire Limited | Greenford | 2005 |