Holiday began her working life as an ancillary worker in an NHS hospital, where she became involved in trade union work for NUPE (now part of UNISON). Following a diploma course at Ruskin College, Oxford sponsored by the TUC and her trade union, Holiday went on to do a law degree at the University of East Anglia. At the same time Holiday began volunteering for an advice centre and, following her degree, became a full-time welfare rights worker and then an employment law specialist.

In 1998 Holiday returned to university to undertake her Bar finals and was called to the Bar in 1999.

Holiday practised as a barrister until January 2004 when, entirely frustrated with the lack of progress towards direct access to barristers made by the Bar Council, she ceased practising and became a freelance employment law consultant. Holiday is the co-author of all the guides on the site and continues to provide her services as a representative on a voluntary basis for a local advice agency.