There may be an analogy with the motor trade here. "You wouldn't buy a convertible sports car in the height of Summer". Well you might, but it would command the highest price.
Likewise with the house market the U.K has its seasons, the spring and summer are the hot spots.
So the unsold convertible will sit in the garage until next year, unless it really MUST be sold.
Likewise there are properties out there which remain unsold. Could be a probate sale (inherited) an ex-rental flat, or indeed anything where the owner needs the money. They don't want it sitting empty over the winter months.
With economic uncertainty and Brexit looming the British do what the British usually do. NOTHING. They adopt the safe 'wait-and-see' policy. But hey, are you missing an opportunity here? If you are in a buying position there are some real bargains out there.
Don't assume the market is falling. With the exception of London most financial predictions see house prices rising now and into the future.
Even in a 'normal' market we sell houses in December that are worth more in the New Year when the sale completes. So how much can you save?
Well how long is a piece of string, but we have seen recent examples of over ten percent. Yes, really, £50,000.00 off the asking price where the circumstances dictated the money was need elsewhere, not stuck in an unsold property.
How are you to know which is which? Well you won't know buy looking at the websites. It might help if you register (personally) with the Estate Agents and explain your position. Good luck with your search.