It could be that the conservatory circuit is causing tripping because the original N-E fault is on that circuit and getting worse. (and just a coincidence that you have changed breakers)
An electrician will be able do an insulation resistance test on the whole installation which should show if there is any fault on the fixed wiring. This (or at least some) IR testing should have been done by the sparks you have had out already. If it's not the fixed wiring, maybe you have been very unlucky with lots of dodgy appliances. Is the RCD consumer unit new? I wonder if it has been properly tested or not and maybe the 1st guy who said it's duff was right after all.
Maybe have a look for an electrician who specialises in testing (or just any good electrician)
An electrician will be able do an insulation resistance test on the whole installation which should show if there is any fault on the fixed wiring. This (or at least some) IR testing should have been done by the sparks you have had out already. If it's not the fixed wiring, maybe you have been very unlucky with lots of dodgy appliances. Is the RCD consumer unit new? I wonder if it has been properly tested or not and maybe the 1st guy who said it's duff was right after all.
Maybe have a look for an electrician who specialises in testing (or just any good electrician)
