Unfortunately, I have little to add beyond what BS3036 has already written.The Electrician has just refused to share the test results with me. He has come back and said - "Am not arguing over some readings the house wiring is well dated and feel free to get a 2nd opinion too . Anything less than the 1 meg is a fail so if it says less than thats cos it is" - and - "Get someone else to go do the test and i will transfer you the money back after i have had a copy of the new report."
Just one thing, in case you feel inclined to give him "one more chance". As BS3036 has said, he did not write "less than 1 meg" on the EICR (but, rather, "<1000"). Is it conceivable that he thinks he wrote "<1" (or, maybe, "<1.000")? Had he written that, whilst we would still wonder why he hadn't given an actual figure, we wouldn't be disagreeing that the two circuits in question definitely 'need attention'. You could therefore, if you wished, tell him that you understand that <1 would be a 'fail', but do not understand why he has written "<1000".
Also, as I've said before, even if the readings were <1 M, that certainly wouldn't mean that a "full rewire" of the flat (which is what you seem to have been applying) would be needed, and wouldn't even necessarily mean that the two sockets circuits needed to be 're-wired', since it might be possible to find and rectify the cause of the low IR readings. Whilst it might be true that the flat would 'benefit from' a full re-wire, there's nothing on that EICR which suggests that anything beyond those two sockets circuits may 'need' re-wiring. Have you discussed with him the possibility of approaches less than a "full rewire of the flat"?
You clearly have had positive past experiences with this electrician and feel some loyalty, maybe even 'affection', towards him but, as BS3036 has said, his current attitude is such that, if it were me, I would probably want to sever my (working) relationship with him! The rather surprising (and 'refreshing') thing is that he has invited you to get a 'second opinion' and seems willing to refund your money (does he mean for all of the EICR?), which is not typical of what one might expect in this situation.
If you don't feel inclined (as above) "to give him one more chance", then I would suggest that you try to find another electrician who would be prepared to fully test just the two sockets circuits - and then take things from there.
From the point-of-view of your current electrician, the silly thing about this is that if (despite what he has written on EICR) he is correct in saying that the sockets circuits require attention, then by behaving as he is he is not only missing out on that work, but possibly also any other future work for you.
Kind Regards, John