A few questions for any doctors regarding germs, viruses and bacteria.?

All of the above can survive at a different specific temperature. They can live in deep ocean, desserts and even in outer space.

Its a lot more complicated than what you described.  Viruses only proliferate inside a host species, so ambient temperature only matters to viruses that infect cold-blooded animals.  Virus survival outside a host is affected by temperature. Respiratory viruses tend to remain viable much longer at cool temperatures and at higher humidifies.  Herpesviruses only survive at temperatures close to human body temperature; while Epstein-Barr virus the causes mononucleosis, survival increases as temperatures drop.  Once frozen, Epstein-Barr virus can survive for years.  

Lemsip and Beechams do not kill viruses.  Their purpose is to reduce the severity of virus symptoms and make people feel a little better.  Warm water helps relieve nasal congestion caused by the flu. 

Bacteria tend thrive at temperatures from around 60 to 100 F, but each bacterial species has its own temperature requirements. 

I don't know who is advising you to keep warm and turn on heat, or why this advice was given, but it is probably unrelated to the proliferation or survival of bacteria and viruses.  

That depends on the mode of transmission and their ability to survive in less than optimal conditions. Many "germs" do not persist in the environment but are transmitted from one person or agent directly to another so the environment does not matter so much.

Being cold for prolonged periods weakens the immune system. Also flu viruses live longer under colder temperatures.