Holding(s) in Company TR-1: Standard form for no

TR-1: Standard form for notification of major holdings

1. Issuer Details ISIN GB00BLDRH360 Issuer Name OSB GROUP PLC UK or Non-UK Issuer UK 2. Reason for Notification An acquisition or disposal of voting rights; An acquisition or disposal of financial instruments 3. Details of person subject to the notification obligation Name BlackRock, Inc. City of registered office (if applicable) Wilmington Country of registered office (if applicable) USA 4. Details of the shareholder Full name of shareholder(s) if different from the person(s) subject to the notification obligation, above

City of registered office (if applicable)

Country of registered office (if applicable)

5. Date on which the threshold was crossed or reached 15-Aug-2024 6. Date on which Issuer notified 16-Aug-2024 7. Total positions of person(s) subject to the notification obligation

8. Notified details of the resulting situation on the date on which the threshold was crossed or reached 8A. Voting rights attached to shares

8B1. Financial Instruments according to (DTR5.3.1R.(1) (a))

8B2. Financial Instruments with similar economic effect according to (DTR5.3.1R.(1) (b))

9. Information in relation to the person subject to the notification obligation 2. Full chain of controlled undertakings through which the voting rights and/or the financial instruments are effectively held starting with the ultimate controlling natural person or legal entities (please add additional rows as necessary)

10. In case of proxy voting Name of the proxy holder

The number and % of voting rights held

The date until which the voting rights will be held

11. Additional Information BlackRock Regulatory Threshold Reporting Team Jana Blumenstein 020 7743 3650 12. Date of Completion 16 ^th August 2024 13. Place Of Completion 12 Throgmorton Avenue, London, EC2N 2DL, U.K.