Last time we went away on our holidays, mum made sure I did not escape my PTU. She did this by planting the door end next to the wall, and plonking her holiday bag on top!! Thus, I could not flip the PTU over and push my way out of the door.
Mum was also impressed that her packing was so light, as normally for a three day holiday, her bag is HUGE. She is determined to travel lighter than she has done in the past.