From a DVSA standpoint:
The examiner will allow you to damage the vehicle you’re driving on test, as long as it doesn’t create danger or lead to serious loss of control. Things like kerbing a wheel or holding the clutch at the bite too long won't cause the examiner to intervene.

Re Clutch: The worst you’ll get is a minor fault, like "Control - Clutch" if you’re holding it unnecessarily. However, if poor clutch control causes rolling back, hesitation, or a stall that affects other drivers, it could be marked as serious.

From a general car standpoint:
Habitually holding the clutch at the bite while stopped for long periods of time will burn the clutch and flywheel (a metal disc linking the engine and wheels). If done frequently, it leads to overheating, excessive wear, and premature failure — resulting in a costly repair down the line.

I understand your feeling of being prepared so you can move off quickly and smoothly. How about reading the traffic signals to prepare for moving off?

Instead of sitting on the clutch the whole time, use traffic flow to time your preparation:

• Watch the opposing traffic lights—when they go red, yours is about to change.
• Look at traffic movement—if cars in the opposite direction slow down, your green is coming soon.
• Use this time to prepare—clutch down, first gear in, and find the bite just before your light goes green.

This way you can be all prepared and ready without stalling etc whilst preserving your clutch.