nightmare....they tried to charge you £1500 when you were working for them? sorted amicably in the end?
in a similar position myself once , although i didnt work for them, the legal standing was as long as i wasnt refusing to pay completely i was entitled to go in and retrieve my car myself and if they phoned the police as long as i offered a fair sum for the work theyed done at that point the police wouldnt stop me taking my car back and it would then have become a civil matter for the garage to persue me for the extra they reckoned id owed.