I had new shower and distribution box installed, electrician gave me installation certificates, though he is not registered under and governing authority, are these certificates valid.

I am not familiar with the scotish system but its similar to the rest of the UK and the electrician should be registered. The electricity safety council have a good website with a leaflet on this for scottish householders; http://www.esc.org.uk/fileadmin/user_upload/documents/public/leaflets/ScottishBuildingRegs1.pdf

in a word , no , if anything goes wrong then it is you who will be responsible and not your friendly electrician . Their argument will be , you should have asked and checked his credentials and not employed him if not satisfactory .

As a Scottish approved electrician myself, the rules and regs are the same nationwide. The only difference is the governing bodies themselves.ANY electrician in Scotland worth his salt will be a member,primarily, of Select or NICEIC. If they are not registered with either, then chances are they are not 17th edition trained. Although some electricians I know,fill out certificates bought from wholesalers(nothing wrong with that)but if they were a bona fide member, they would use the certificates to prove it.If they claim to be Select registered,you can visit the Select website to verify this. Just ask for their membership number.Hope this helps, Regards, Mark Sparkright Electrical Services