Been there today, removed light fittings, had cpc so no problem installing the standard fittings.  I have seen the main earth conductor connected to the main earth terminal and from there to the CU and to the water and gas pipes, checked continuity from the main earthing terminal to the CU (earth) and to the pipes, reading about 0.10 ohm, sounds good to me.
Continuity of cpc was a hige (I checked 2 circuits), one was 2.88 ohm and the other 1.04 ohm, 6A old type mcb (PROTEUS), Zs allowed is about 6.7 ohm (acording to BS7671).  
Had difficulties in checking Zs, probably something wrong in my procedure...
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Yes you might be right but the customer asked for a certificate as she does not want problems with the buyer, (a builder).