Plug in MCB's?

Anyone used plug in type MCB's?
My energy supplier contractor put in a 'over the top' [£810] estimate to replace my Wylex wired fuse fuseboard circa 1978-82 the fuses with the colour dots white 5amp Blue 15amp and Red 30amp. It works ok it's just a pain wiring up one when it blows. And supplementary bond 4 pipes in airing cupboard.
His tick sheet for the visual inspection gave the Main earth,supplementary earth and the fuse boards as in need of urgent attention yet he never put a meter on any of the earth points or the fuse board so how would he know they need URGENT attention. I am not having him do it any way. I think he thought 'He's an oldie I can screw him for a wedge'...wrong I'm wiser than he is, been their done that, I re-wired my London house many yrs ago including fitting an new fuse board obviously well before Part P regs and it all passed.

He wasn't aware I had a friend who does testing for a living test it months ago and the earth was up to standard, that's why the shark isn't getting the job. I'd like to know how many oldies he's stuffed up, a company was featured on Tele doing the same thing replacing fuse boxes at exorbitant prices no wiring just fuse boxes and some didn't need changing from description and age. One even needed re-wire but they just changed the fuse box.

Opinions please on the following MCB's
Wylex do a plug in type MCB and I found site that sells them £7.25 each or £68 for 10 +postage a big saving.
Is replacement as easy as pulling out the old one an plugging in the MCB or does the fuse carrier also have to be changed?
it's a Wylex fuse board....
Rob