"Unfortunately TUPE does not apply here as BC are buying out all of the shares."
Incorrect. It has nothing to do with shares or cash. TUPE is about Transfer of Undertaking - BC is legally bound to abide by the law. When an entity acquires another the employees of the acquired entity are protected by TUPE
"A transfer of undertakings (TUPE) occurs when either a business transfer or a service provision change takes place. When a business moves to a new owner in one of these 'relevant transfers', the Transfer of Undertakings (Protection of Employment) Regulations 2006 (TUPE) currently protect the entitlement of UK employees to the same terms and conditions, with continuity of employment, as they had before the transfer."
https://www.cipd.org/uk/knowledge/factsheets/tupe-factsheet/
Stop spreading misinformation.