OP, although I don't know the answer to your question, I sense you not getting good advice on this thread. A lot of supposition is going on.
I did a self build 10 years ago. Never got any certificate of compliance. (I've only vaguely heard of such a thing). I never did anything about title ... I have title deeds to the land, that is all. I have no mortgage. I'm not thinking of selling any time soon, so if there's a problem I'll deal with it in my own good time.
So, who says your brother needs a certificate of compliance? Is it the bank who is belatedly trying to make sure the title to the property is good? Or is the solicitor doing this off his own bat, and if so why? However, the main question is -- what are the consequences (for your brother, not anyone else) of not doing it? If there are no immediate consequences, then he can just tell whoever it is to go stuff themselves (perhaps not in so many words). Just tell them he hasn't got the money and he's not doing it.
Just as an aside, I would find the concept of certified compliance quite hilarious in an ironic kind of way. I had restrictions on everything from wall and roof colours, to house type, orientation on "existing building line" (even though there was nobody within hundreds of yards of me), type of planting etc. etc. I complied with every detail. Now I have close neighbours on either side which the planners allowed to build utterly different house types, different colours, reoriented to face a sea view etc. etc. Both overlooking me in a semi-unpleasant way. I've half a mind to demand a certificate of compliance with their own policies from the planners. Complete joke.