estate agencies accepting suitcases of cash was a shaggy dog story
Indeed not. Likewise car dealerships allowing you to pay for a shiny new Bentley with a big suitcase of cash. It's not explicitly illegal to do so but then the dealership/estate agent has to prove the source of the cash to the anti-money-laundering chaps.
In short, too much hassle. Computer says no. Do not pass go, do not collect $SHINY property/car.