People do get very worked up about this subject, and for no good reason. There are a lot of rumours, guesses and plain old BS running about this. It comes down to two things, the DNOs won't get involved because it will cost them, so the sparky working on the installation must deal with the situation.
There are two ways to do that:-
1) Spend ages on the phone talking to Mr or Mrs Don't-know, after sometime you may get passed through to Mr or Mrs Don't-care. If you persevere and resist the temptation to issue death threats or launch the phone into orbit you may get an appointment booked for some weeks hence.
2) Cut the seals off if they are present and look at the fuse carrier. Using your judgement and experience* decide if it's safe to pull.
a)If it is pull all fuses, switch off MCBs, RCDs and the main switch. Then get your gloves on and a face sheild(not compulsory, but definately a good idea) pull the fuse, do the work(including a DP isolator if you want to be nice to future sparks), replace the fuse fit new seals, and get on with your life.
b) If it looks insecure, cracked, crumbly or dodgy contact the DNOs emergency line and tell them that there's a burning smell coming from the fuse/service head. When they turn up to sort that out ask them to fit a DP isolator which you just happen to have handy.
* If you don't have the knowledge or experience to judge the fuse condition don't cut the seals. Your prize for showing good sense will be in two parts. Firstly you potentially get to live a bit longer and/or avoid looking like Freddy Kruger for the rest of your life. Secondly you get to experience the joys of a telephone conversation with a DNO customer 'help' line.
I am quite happy to state on an open forum that I have removed DNO seals and fuses, and that I will continue to do so. I always fit new seals when I'm done, and I always contact the DNO if the carrier looks like it's going to give trouble. If any DNO wishes to challenge my decision to save them money, and avoid working live then kiss my, er, I mean, please feel free to contact me with a court date if you can find a solicitor stupid enough to challenge HASAW and ESR along with European law, and common sense.