I found shortcomings from both electricians, so I am not going ahead with any one of them.
One was the attitude to replace RCBO with MCB if fault can't be rectified, instead he should have said that we must rectify the fault as that can be dangerous.
The second one is the earth bonding. When I told him that the supply pipes are plastic up to the house boundary he said he will leave the water pipe but he will upgrade the bonding to gas pipe anyway.
Strima said that you guys will calculate in this scenario if bonding is required. I read about bonding in the following article.
So it certainly makes a case to do proper assessment and calculation and then bond if required. So that is another thing
I will take few more quotes now because now I know what should I ask. I am fairly sure that old cables and sockets(MK brand) are in very good condition. The only sockets which I have doubt are relatively new ones fitted in the kitchen during kitchen refit about 9 years ago. They are of Lap. One was causing sparks during on/off and blew the fuse. I have changed 3 single Gang sockets with Schneider sockets. I will replace the other sockets in the kitchen too. Is Schneider fine or should I get the MK brand sockets.
May be I should just get an EICR first and if there is a need for rewire then sort that first at the first opportunity and then at the same time do the CU upgrade. If no faults then just do the CU upgrade. The new circuit in the kitchen can wait until that time.
Btw, a lot of you are emphasising on SPDs. I am still not convinced of their benefit in an average city house. Anyway if one has to go with SPD then is it allowed to mix different brands in a CU or not. I know you can't mix different brands RCD/RCBO/MCBs. Whatever make is the CU, it should be the same make components. So is it same for SPDs. I am asking this because there is huge difference on price of SPDs between different Makes?
Should I also go with AFDD as that provide additional protection too?
Thanks for all your help