Trevor what is your role or duty in respect of this work? If you are responsible for safety management or are liable to be held responsible in any way if things go wrong I would suggest you can insist on having the correct proofs of training and RAs etc prior to work starting and refuse entry until documents have been produced and to insist RAs and method statements are followed. I would advise that you don't approve these documents but do speak out if there are obvious inconsistencies or unsafe work practices. If you aren't likely to be held to account and can be over ridden by others, I feel you should make seniour management aware of your concerns, preferably in writing or email, if it goes wrong then you will have done all you can. When I was managing construction sites I learned to insist that the correct documentation & proof of training was in place and have refused permission for work to continue until it is all available. I have also been caught out by not checking only to find non competent workers doing high risk work. Your company should have done competency checks on the contractor and considering the high risk nature of the work these should have been quite thorough, the company should also insist that contractors provide the correct paperwork.

Is there no permit to work system? A key part of issuing a permit is contractor competency etc...