In reply to The New NickB:
> Are you sure about that?
Well it's 35 years since I was building conservatories but I'd guess the heating engineer was up to date. 30secs with Google gives you, courtesy of Planning Portal;
"However, conservatories are normally exempt from building regulations when:
They are built at ground level and are less than 30 square metres in floor area.
The conservatory is separated from the house by external quality walls, doors or windows.
There should be an independent heating system with separate temperature and on/off controls."
As I wrote, contact the local planners.