L322 04 TD6 FBH

Hello. I have an issue with the FBH on my RR. I bought a remote to switch it on, the remote has been synced and it switches the FBH on. Currently the outside temperature is around 0.5°C, you can hear the FBH turn on when you unlock the vehicle or open a door. It switches on with the remote and when it is on, it stays on and sounds as if it is working (sounds like a boiler), the only issue is that the interior temperature does not seem to increase by much. It's still cold when I go to the car, is this normal?
What are other people's experiences with the FBH?
Does it heat the interior up to a comfortable temperature?
What diagnostics can I do?

Thank you
Qasim

Mine kicked in for the 1st time this morning.
I understood the FBH only warms up the engine coolant to aid cold starts & heat the engine up to reduce emmissions. The interior will only warm up (quickly) once youve started the engine & the HEVAC is in operation.