However there is some limited statutory protection, under the Pensions Act 2004 and the Transfer of Employment (Pensions Protection) Regulations 2005.
In short, if your old employer provided a pension scheme, your new employer must provide some form of pension to eligible employees. It need not be equivalent (and it can be worse) but it must meet a minimum standard.
You can find information about the minimum standards on the website of the Pensions Advisory Service, which has a helpline: 0300 123 1047.
Employees who transfer compulsorily from the public sector are entitled to pension protection under a non-statutory policy known as Fair Deal. They must be offered continued access to their existing public service pension scheme, instead of a 'broadly comparable' private pension scheme. Ex-public sector staff whose employment is compulsorily transferred a second time to a new service provider (so called second-generation transfers) are also covered.
Fair Deal guidance is available. The new rules apply to employees transferred compulsorily from central government departments, agencies and the NHS, as well as maintained schools (unless they are covered by other local government arrangements) and academies.
Fair Deal protection will be lost if an employee voluntarily moves to a different role with new contract terms.