Answers:
You can use a coarse sandpaper or a sanding block to carefully reapply the excess bonding around the socket’s creating a recessed area for finish coat
If the wall is in a bad state with some parts down to the brickwork, it's generally advisable to repair the damaged areas first. fill in the holes with an appropriate filler or patching compound, ensuring a smooth and level surface. once the repairs are complete and dry, you can consider plasterboarding over the repaired area for a clean finish. if the damage is extensive or the wall is in poor condition, you may need to assess whether it's necessary to remove everything down to the brickwork for a more thorough restoration.
Building regulations and planning permissions vary, and there might not be a specific time limit for rendering mentioned in those regulations. however, you may want to check with your local planning or building department to see if there are any conditions or agreements related to the appearance of the extension.
if there's a significant deviation from what was approved in the planning permission, you may have grounds to bring it to the attention of the local authorities. it's advisable to consult with them to understand your rights and options in this situation.