Always document what you do and find. Notes taken down, photos on camera, etc, for all jobs if you can and
not just cases the worry you. It comes in handy for any reports you need to write or customer questions that may come later, such as checking parts to quote for remedial actions, etc.
Of course if there are situations that bother you then take extra care and don't be afraid to ask for advice from other sparks as well. At some point it comes down to a judgment call on what is 'safe enough' not to lose sleep over, and if you can tell those in charge of any decisions what the risks are and how serious they might be then I expect the majority will take your advice and either leave it off, or plan for remedial action if it is not posing an imminent danger.
But if you do have the horrible feeling that someone is going to ignore you on something you are really not happy with then generally either the H&S executive can be informed (industrial) or the local authorities (shops, pubs, etc), but check here for any odd cases:
Authority - the type of workplaces HSE is responsible for and those where Local Authorities have responsibility.
www.hse.gov.uk
At the very least you have then both informed the installation owner/operator of the risks in writing and passed on concerns about their attitude to safety to the body ultimately responsible for any enforcement action.