TUPE
TUPE is not only about business sales. Charities meet it when they merge, when they take over a service from another provider, and when they lose a contract to one.
Where TUPE applies, affected employees transfer to the new employer on their existing terms, with continuity of service preserved. There are information and consultation obligations on both sides, and dismissals connected to the transfer are usually unfair.
The trap is discovering TUPE after the decision rather than before. Check it during due diligence, and factor the inherited liabilities into whether the merger or contract makes sense at all.