As with United States huge amount of post war demand for major appliances came from a few key sources. Pent-up demand due to shortages caused by the war, creation of new (or rebuilding of) homes, rising affluence, etc...
For various reasons some areas of Europe kept going well into 1960's and 1970's as power house of appliance manufacturing. Changes were coming however from several fronts.
European common market meant local appliance makers had to compete with things coming in from other parts of Europe. Japan and other Asian nations also rebuilt and retooled manufacturing after WWII and by 1970's or so were exporting sewing machines, electronics and other bits to USA and Europe shaking up local manufacturing.
In USA and most parts of Europe costs of production (quite high in comparison to Asia) meant things couldn't be offered a prices to compete with flood of imported goods. R&D and other bits require capital, if a company doesn't have access and or otherwise cannot invest in growth it will either die or become an attractive takeover target.
Some European companies simply died or experienced difficulties due to issues with founder and or his family.
18 June 1968, Lino Zanussi and other key members of the company’s management, all died in an airplane crash. This came at worst possible moment for Zanussi and by 1970's company was having difficulties. Eventually best solution was deemed to partner with a much larger company, enter Electrolux...
https://www.electroluxgroup.com/en/history-of-zanussi-a-reflection-of-the-italian-wonder-28262/
https://time.com/archive/6807981/italy-household-revolution/
As for UK it would take volumes to explain why her manufacturing went into decline. Happily others have researched that issue so won't have to bother blathering on...
https://www.jbs.cam.ac.uk/wp-content/uploads/2023/05/cbrwp459.pdf
Very basically whole "Export or Die" mantra of post war GB coupled with lack of investment and government policies that chose winners and losers did it to many sectors of UK manufacturing.
https://www.britishpathe.com/asset/208259/
Endless actions by trade unions and so forth didn't help UK's manufacturing base.
Bad as things were for manufacturing in UK they were about to get worse with arrival of first government of Margaret Thatcher. Endless monetarist policies, high interest rates and an overvalued currency all hit the manufacturing sector particularly hard. UK's exports became uncompetitive in world market, while at home UK goods became uncompetitive domestically against imported goods.
Fate of some UK manufacturing was simply decided by events elsewhere.
While iconic in British appliance history Hoover was an American company. Thus forces well beyond shores of Britain affected Hoover's manufacturing in UK.
https://en.wikipedia.org/wiki/The_H...e Hoover family,by Maytag Corporation in 1989.
When Maytag bought Hoover earlier this year, it was a homemaker's dream--the marriage of two businesses that started out producing appliances to make housekeeping tasks easier in the early years of this century.
www.latimes.com