On Tuesday afternoon, six women, all Polish, sit around a table in a small cafe near Waterloo Station in London. They are at the end of their shifts as room attendants – chambermaids in a previous era – at the four-star Park Plaza Hotel County Hall, a five-minute walk from Westminster. They look exhausted.

Cleaning at their hotel, like many services, is outsourced. Four months ago, as employees of Hotelcare, “where first-class service comes as standard”, they were paid £6.50 an hour to clean 13 rooms in eight hours, every day, five days a week– a long way short of the London living wage of £9.15 an hour. Then the contract was taken over by another cleaning services company, WGC, “servicing over 10 million hotel rooms a year”, includingare paid between £2.30 and £3.75 per room.

One woman tells how she worked for a cheaper chain and, illegally, was paid a piece rate – £2.17 a room, 25 rooms a day. Another says that if her allocated rooms are not completed in time because guests are late departing, she has to work the extra time, unpaid.

Ewa Jasiewicz outside the Grosvenor House hotel on Park Lane, London. Photograph: Richard Saker for the Observer

Ewa Jasiewicz, 36, is one of two part-time organisers who, supported by Unite, have since January been working to unionise hotel workers, using a system developed in New York that has proved highly successful, and has forged links with other unions as well as faith and community organisations.

Many London staff will not picket a hotel for