Remember an airing cupboard stuffed with a new immersion heater tank, without an inch to spare at each side, obviously much bigger than the original and with a great big pressure vessel on top. My problem...'can you sort my alarm out'. Called to find that his external alarm sounder kept 'going off' when he had a power cut.
The panel was directly behind the pressure vessel. Really tight but not totally impossible, I told him that I'd return the day after with a new battery. He said it was ok, he'd sort it.
Got a call the following morning asking if I could give him a lift as it was a bit hard work. Got there to find no cover on the panel.....dropped it down the back of the tank trying to remove it.