Make sure the area around the cutout is clear of any debris inside, also check the spring clip is not hitting a joist and also check the height of the spring clip which you may be able to adjust by moving it up or down on the side of the fitting
I was going to list all the other things but got bored tapping the keyboard. It doesnt stop there, time sourcing materials, paperwork, PPE, Regs books the list goes on, so 0.05% is not a lot.
An hours work....including 4 years training, diesel, time traveling to job, £350 worth of tools, certificate and knowledge that it is safe......He is not charging enough
When you say insulation do you mean Selotex? And when pushing the fitting up have you tried feeding the cables up and out of the way instead of just pushing them straight up?
What size cable feeds this circuit, if its a minimum of 4mm just make this a 32a radial circuit using 4mm cable to each additional socket as long as all appliances are on a 13a plug as you stated
Anyone that actually sparks for a living knows you should not have an immersion on a 13a sfcu even if it works out at 12.6a load, as running it for the amount of time it takes to heat the water will cause the unit to get very hot and after a while will cause problems. Should be on its own...
I don't mind people being told YES you can do it yourself and issue your own cert and do all the testing yourself, Because in a couple of weeks time when everything starts going bang I can charge them a good amount to put it all right and it's all down to the fact they should have got somebody...