Garage part conversion to utility

Hi, just need some advice regarding building regs/planning.

Current double garage with an external door on the back wall leading into the conservatory which was added prior to me owning the house. The conservatory also has a single French door into garden and another external door that leads into the kitchen.

Looking to convert the rear section of the garage (about a third of the current garage area) into a utility room with a sink and space for washing machine on one side. The remaining area in the new space will be for storage mainly.

Plan is to add a stud partition wall with a doorway to connect remaining garage space to new utility.
No plumbing or wiring will be in the new stud wall.
On the other 3 walls (brick) of the new space plan to batten and screw plasterboard with existing wiring/plumbing behind.

Existing power sockets on the walls will be re-used in new walls.

Existing waste, hot and cold water pipes (currently run along garage wall and go through into downstairs toilet on other side of the garage wall) will be used for sink/washing machine.

All of the new walls will be insulated. Also plan to fix studs to existing ceiling (laterally fitted to existing ceiling joists) and insulate/plasterboard.

Then all walls and ceiling will be skimmed.

Floor is concrete and sits about 6 inches below the conservatory floor level. I plan to tile over this.

Question is does this project need building regs and/or planning permission?

Thanks in advance for any advice offered.

Think you may need a building notice/regs, probably not planning.

If you insulate (walls/floor) you will need to reach today's standard.
I helped a family member do theirs, it was already a cavity wall (filled) and still had to put 75mm insulated plasterboard on the inside.

Any additional electrical work may need sign off too.

Thanks for the reply Mr Chibs.

I was planning to use CLS stud work so I would probably only get a maximum of 50mm insulation behind the boards. Also, I hadn’t planned to insulate the floor - is this necessary? I’m not adding heating in the room.
Also what would be needed in terms of ventilation? Could I put a vent into the partition wall between the new utility space and the garage space or would it need to be through the brickwork on an external wall?