OP, the UK's Equality Act (October 2010) protects breastfeeding women.
What does the law say?
The new Equality Act says that it is sex discrimination to treat a woman unfavourably because she is breastfeeding. It applies to anyone providing services, benefits, facilities and premises to the public, public bodies, further and higher education bodies and association. Service providers include most organisations that deal directly with the public. Service providers must not discriminate, harass or victimise a woman because she is breastfeeding. Discrimination includes refusing to provide a service, providing a lower standard of service or providing a service on different terms. Therefore, a cafe owner cannot ask you to stop breastfeeding or refuse to serve you.
Where can a woman breastfeed? You are protected in public places such as parks, sports and leisure facilities, public buildings and when using public transport such as buses, trains and planes. You are protected in shops, public, restaurants and hotels regardless of how big of small. You are also protected in places like hospitals, theatres, cinemas and petrol stations.
This link is a PDF download, but it has info in it..