17th edition work on my fuse board

Technically, you only need to upgrade the devices protecting the circuits that are being altered. It sounds like you are having a few circuits altered. If any of these are not protected by your RCD, then yes they will require an upgraded device. If any other circuits which are not to be altered are not protected by your RCD, then they are very likely to fail the condition report you have requested, and so it is probably sensible to change all unprotected MCBs for RCBOs. Sounds like your last quote was the good one. Always make sure you are dealing with competent installers, who are members of approval schemes such as the NICEIC Approve Contractor. If you truly wish to have your consumer unit upgraded to meet current guidelines (BS:7671 2008 A3 2015), then it should be replaced with one that is made of non-combustible material. The cost of installing a split-load board A3 board when offset by retro fitting your existing one with RCBOs may well be worth inquiring about. Your local, competent and approved electricians are best placed to advise you on price, and you should expect installation certificates and building control notification for this work.

The first thing to do is get an electrical installation condition report done, then you will be aware of any potential issues that may not be obvious without doing some tests. It would be impossible to give an estimate of costs for this job without a 'survey', for example are the floors concrete/floorboards/wayrock? are the walls drylined/plastered over brick etc. Are the circuits fed from the floors or ceiling which has an impact on the amount if chasing. What about making good /replastering If you wanted your 'fuse board' up to current regs then it will be a new board as i assume your existing one does not meet with the latest standards, in that case it will not matter regarding rcbo's. Also it will have an impact on the age of the house and the age of the electrical installation, i will guess that other work will need doing such as earthing upgrades etc. You will have a good idea of the costs after having four quotes, also effects prices in your location ie the south east and london are much more expensive than the north, check out the which magazines price guides, that is a good yard stick. This sounds like a partial rewire not something you can do in a couple of hours. You have to remember when an electrician does a job like this and signs it off, he is taking responsibility for the complete installation and therefore he must be happy with what is already there. Generally speaking 'you get what you pay for'. Get a quote on paper that way you and your electrician have some sort of 'protection' as to what was included in the estimate and what was not.