a bunch of sparkies, who were rubbing their hands with glee about all the new regs comming in, they said they were going to make a fortune.
Doubtful, as notification of works had no effect on the charlatans who didn't bother with doing the work properly, and for everyone else it just increased the costs of doing those notifiable works. The only people making loads of extra money are the Part P competent persons schemes.
Electrical wiring is now a closed shop,
It isn't. All Part P did was make certain types of work notifiable to building control, in the same way that replacement windows, heating appliances and many other things already were.
Nothing changed regarding who is or isn't allowed to do electrical work.
which is pushing prices higher and higher.
There are vast numbers of 'electricians' happy to charge people next to nothing.
Quality work costs more.
The only contribution Part P made to the mess was to encourage various organisations to offer dubious training courses so that people with zero experience and who had never even picked up a screwdriver in their life could become 'qualified electricians' in a week or four and then go out and wreck people's electrical installations.
However, most of my circuits enter the back of the CU, through large rectangular holes, with rounded ends. Can you get anything to properly seal these holes and cables?
It's not necessary to have large holes in the back. Smaller holes can be made. Cables can enter via other surfaces.
There are various ways to seal them such as grommets, gland plates, individual stuffing glands, intumescent mastic, intumescent pads and so on. All depends on the exact situation.
There is no such thing as an '18th edition consumer unit' - that's just a useless marketing term created so that manufacturers of consumer units can sell more of them. Often used by DIY sheds that are selling non-compliant junk.
As for replacing it - the correct process is:
- Full inspection and test of the whole installation
- Repairs where required, which on an older installation will be almost inevitable.
- Main bonding is often undersized or non-existent so that would need to be installed/replaced.
- Once that is done, you can remove the old consumer unit and install the new one. New tails included.
- Then it's testing the circuits for a second time.
On a small installation with only a few circuits and no major problems, it's a full days work.
For larger installations and those with various defects, considerably longer.
For situations where the existing supply isn't adequate for the load, or has some other problem - wait until the DNO has upgraded or repaired it.
How much would you expect to pay - both for the consumer unit itself and for someone to install it properly?