The design and construction of the machine would hopefully have been independently verified to the standard you mention (EN or IEC version - same thing) by an accredited laboratory, such as Intertek or SGS or UL or BSI etc. or if your German machinery manufacturer has the in-house capability, by the QA function in the ISO 9001 German company, and a Declaration of Conformity issued detailing the Directives and standards the machine complies with. (electrical safety, mechanical safety, electromagnetic compatibility, maybe environmental, ROHS etc)
If you are working inside the machine I would expect what you do to be covered by the manufacturers procedures/ installation instructions, and for you to be keeping installation records in line with the manufacturers installation checklist or procedure. I would expect such instructions to include details on incoming supply, protection and cable sizes, and any special requirements. As you say, once you get past the cables feeding the machinery, you are in BS 7671 territory.
There are also Health & Safety regulatory and safety standards, and perhaps food hygiene standards, to consider.
If you are not an employee of the German company, but an employee of "the local hub" and you are not being provided with any of this, I would expect your direct employer to have a process in place to provide and monitor the installation, and be certified to ISO9001 to continue the machines installation history/records. If that is the case, the Quality Manager (or his/her department, or Quality Representative) of whoever is employing you should be on this, and providing documentation and guidance. If the 'local hub' is just being set up now, part of that should be implementing company procedures, including Quality Assurance, that will ultimately define installation processes and keep the necessary records. I would hope this would be supported, or even provided, by the German manufacturer, including access to standards and machine documentation.
If there's no infrastructure supporting you, that's an undesirable situation. Usually reputable machinery manufacturers are keen to have some control over their installations and installers, and I would expect some flow of information/ documentation/ training etc. to be coming from them. Perhaps it is, but not getting to you?
One reason why this is so important is that electrical and mechanical safety standards have become more risk based over the past decade or two, and risk assessments are an integral part of machine design, hopefully extending through to installation. So somewhere there will have been brainstorms, hazard analysis and risk assessments trying to predict what needs to be done, including during installation. I would have expected such activity to have produced instructions, if not checklists, for installation. An effort should be made to obtain anything like this!
Working inside the machine puts you in the front line if anything should go wrong, so you are right to be concerned about it.
If your enquiries don't elicit anything useful, and you are pressed into getting on with the job, I suggest as a minimum you keep a log book detailing what you did and what and how you tested, along with photo's.
I just hope you don't end up being the person asked to write the UK installation instructions!
Edit PS: I am aware that the accredited test houses have access to sets of checklists for the various machinery safety standards, so for the particular parts of EN60204 that apply to your filling and packing machines etc. there are huge checklists for compliance with those standards. A far as I'm aware they are not in the public domain, but finding out who did the machine approvals might lead you to someone with access, in which case you (or preferably they) might be able to cherry pick those for salient points.
