- BAKER & O'BRIEN (UK) LLP- OC340683 - Incorporated on 8 October 2008 
- KIERAN O'BRIEN LTDActive - Proposal to Strike off- 09558254 - Incorporated on 23 April 2015 
- GARETH O'BRIEN LTDActive - Proposal to Strike off- 09563941 - Incorporated on 28 April 2015 
- O'BRIEN&WILSON LTDDisolved- 08945281 - Dissolved on 12 September 2023 
- O'BRIEN SEARCH LTDDisolved- SC631445 - Dissolved on 21 June 2022 
- BARNET O' BRIEN LLP- OC323689 - Incorporated on 6 November 2006 
- KJ O'BRIEN LIMITEDActive - Proposal to Strike off- 04136109 - Incorporated on 5 January 2001 
- SAWYER O'BRIEN LLP- NC000553 - Incorporated on 30 September 2009 
- BRIEN & BRIDGE LTD- SC709940 - Incorporated on 21 September 2021 
- PM O'BRIEN LIMITEDActive - Proposal to Strike off- 10175022 - Incorporated on 11 May 2016 
- BONITA O'BRIEN LTD- 12398880 - Incorporated on 13 January 2020 
- R.J. O'BRIEN (UK) LIMITEDDisolved- 04299065 - Dissolved on 25 April 2023 
- A. O'BRIEN SPINES LTD- 09273931 - Incorporated on 21 October 2014 
- E O'BRIEN IT LIMITEDActive - Proposal to Strike off- SC558335 - Incorporated on 22 February 2017 
- O’BRIEN & SON AUTO’S LTD- 13451384 - Incorporated on 11 June 2021 
- ARTHUR & O'BRIEN LTD- SC811668 - Incorporated on 26 May 2024 
- BRIEN BRICKS LTD- 16124030 - Incorporated on 9 December 2024 
- PASQUALE DE SIMONE LTDDissolved- 08811763 - Dissolved on 22 May 2018 
- O'BRIENS LIMITEDActive - Proposal to Strike off- 03712395 - Incorporated on 11 February 1999 
- O'BRIEN & CO LIMITED- 07475894 - Incorporated on 22 December 2010