I woke up at 7am and the house was at18C with no heating. Outside was about 12 C so still in just a sleeved vest and trousers outside in the garage still fitting the new flooring.
rarely any frost here at sea level but does happen sometimes in Winter.
Low content boilers are often 120,000 BTU so twice as much heat as the old back boiler. As long as the installer did a very good flushing of the radiators several times, it will last at least 10 years. Those fitted without flushing tend to fail much faster. Normally, if its a job you are paying for, you should have changed radiators to low content type with fins. The free boilers offered to low paid or unwaged or pensioners on pension credits etc rarely get the radiators changed as it normally done at the cheapest cost.
Combi boilers are supplied free in many circumstances but might be means tested and if you are money rich, you would pay.
Some of the Vaillant boilers i used to work on lasted over 20 years but did have many parts failures. A rubber bag at the back contained in a steel shell perishes at 10 years, pumps were very costly and flue fans often failed at 3 years. Those boilers supplied 18 radiators and 10 basins plus 2 bathrooms, hard worked