Where there is a change to your lease that is unacceptable such as the introduction of parking contractors / permits, the first thing to do is to check your lease.
In the case of Gordon v Elizabeth Court (Bournemouth) Ltd , Mrs Gordon's allocated space was taken away and parking offered on a first-come, first served basis. She argued that this change was material in that it would lead to a devaluation of her property. It was also being imposed against her will. The High Court ruled that her right to this space could not be taken away and so the scheme was abandoned.
See article: http://www.bournemouthecho.co.uk/news/districts/bournemouth/9960349.Resident_wins_High_Court_fight_over__free_for_all__parking_scheme/