Hi Sean
I don’t know about gutter vac's but I am a safety professional and I ran a cleaning company for more years than I care to remember.
If you write down some bullet points of likely hazards, I will write a Risk Assessment and Method Statement (RAMS) for you to review and then it would be revised so you have a complete document.
I will do this for you free of charge.
These RAMS must be dated forms and reviewed every 12 months or sooner to comply with the law.
I hope this helps
Steve
Trainer