Other measures taken to impound aircraft until payment was made included, again at Heathrow in the late 1980s after carrying out a heavy check on a Mediterranean Express BAC1-11
[it may have been this one:
https://abpic.co.uk/pictures/view/1068604] the aircraft sat outside the hangars for a good while waiting to be collected until payment was received and on parking the aircraft batteries and nosewheels were removed just to make sure it didn't get flown out before full payment was received...