If the company you work for is changing ownership your current employment contract could be protected under the Transfer of Undertakings (Protection of Employment) Regulations, known as TUPE. Tupe claims.
Both business transfers and service provision changes can be protected by these rules but if the procedure is not followed properly you could have a basis for a TUPE claim.
To gain TUPE protection, the transfer or change must be from a UK-based company, but it does not matter how big that company is. Check out equal pay claims.