OSB GROUP PLC                                        
ISIN: GB00BLDRH360
05 December 2025

LEI number: 213800ZBKL9BHSL2K459

OSB GROUP PLC (the 「Company」)
Transaction in Own Shares

The Company announces that on 04 December 2025 it had purchased a total of 17,504 of its ordinary shares of £0.01 each (the "ordinary shares") on the London Stock Exchange, CBOE BXE and CBOE CXE, through the Company's broker Citigroup Global Markets Limited as detailed below. The repurchased ordinary shares will be cancelled.

The purchases form part of the Company’s share buyback programme announced on 13 March 2025.

Following settlement of the above purchases and cancellation of the purchased ordinary shares, the Company's total number of ordinary shares in issue shall be 356,759,344 ordinary shares.

No ordinary shares are held in treasury. Therefore, the total number of voting rights in the Company is 356,759,344.

In accordance with Article 5(1)(b) of Regulation (EU) No 596/2014 as incorporated into and implemented under English law (including by virtue of the European Union (Withdrawal) Act 2018), the detailed breakdown of individual trades made by Citigroup Global Markets Limited on behalf of the Company as part of the share buyback programme is set out below.

This announcement does not constitute, or form part of, an offer or any solicitation of an offer for securities in any jurisdiction.

Schedule of Purchases – Individual Transactions