Cannot help it, but had a chuckle when reading the responses to the question asked.

Is it legal to do a coc on your own property ? ...... yes it's legal.

Would I pay another electrician to replace a burn't circuit breaker or socket outlet in my house ? The hell ....... no.
Would I pay someone else to do a coc on my house, should I sell it ? The hell .. no.
If I were a motor mechanic, I wouldn't pay someone else to fit new brake pads neither.

You should, in any case, be doing ALL coc's as if the chairman of the ECA is buying the property. Then you're covered.
As for vested interests. Everyone has a vested interest. The electrician contracted by the estate agent or attorney also has a vested interest.
The more faults he finds, the more money he makes. Be honest, who hasn't seen unnecessary repairs being done in order to inflate the price.

My advice is. You are suitably qualified and registered to do it, so save some money and just do it.