No. Sorry - I mean you can, by all means - but why isn't he certified?
That's what you have to be asking yourself (and him)
We had one who was 'in the process' of certification (as a competent person). Turns out he wasn't there yet - so he was unable to sign off his own work, cue us having to pay the council to send a chap out and test it all over again which took a whole day.
Ours was also very sweet but he was flaky as anything, and loads of stuff was wrong, forgotten to finish, the sockets he had marked places for were nowhere near the marks, at times - and the MESS he left with th lath and plaster was horrifying.
He even used plastic boxes in crumbling plaster walls, which came out when you pulled a plug out.
Horrific.
I had to redo all the socket back boxes, myself, all the plastering over channel/conduit, we're still finding errors now.
My advice is to get the oldest, most experienced, most qualified person you can possibly afford.
Simply put if he isn't certified as competent there is a reason for that, and you don't know what it is - but whatever it is you will still need to get a third party in to certify his work, and they'll have to be informed in advance, and it's a really blimming hassle.