The UK regulations are not concerning norovirus but Hepatitis C. The nozzle of the pump does not need to be immersed in the beer to transfer germs, merely letting the nozzle contact the inside of the glass is sufficient. There is a requirement to issue a fresh glass with every pint of draught beer.
If you insist on having a glass that has 'warmed-up' or that is in your favourite style then don't hand it in when ordering your pint.
Transfer the pint from the 'fresh' glass to the one you're already using & hand the 'fresh' glass back for washing.
Simples?