In reply to coolbert:
> Ah, i meant working at height.
Which isn't working at height? Erm.. you've lost me. You mean it's a DiY project?
Otherwise it doesn't matter whether you're working for a company, some other kind of organisation or a individual and it doesn't matter whether you're volunteering or being paid - it's still work.
But even if it is a DiY project, which would mean you're unlikely to land yourself in legal trouble at least, you need to have a proper think about whether you really know what you're doing. Would you be happy to just solo it? No? In that case it's probably a bit too likely that you're going to fall to be working in fall-arrest (as opposed to finding a way to prevent a fall). We're not talking sport climbing here, falling off is not ok.
Ok, leaving this aside for a mo..
> So I will still need to choose my own system.
You've skipped several stages of the planning/risk assessment process and just assumed that you'll be working in fall arrest, exposed to a significant potential fall, in which the lanyard you're relying on is likely to be loaded over a sharp edge. These are all things that you should be looking to eliminate - especially that last one which is a real killer. (Even if that isn't particularly cheap/convenient.)
Is the thing you're planning to do really necessary? Is there a way to achieve the same objective without getting access to whatever you're trying to gain access to? Use a different gizmo, install it somewhere else, etc.
Assuming not then.. can you put scaffolding up? Can you hire a MEWP?
Assuming not then.. can you use work restraint or work positioning instead of fall arrest? If the anchors you've mentioned are not suitable, can you install more suitable anchors, either temporary or permanent?
These are all rhetorical questions btw - I don't need or want answers to them, they're the questions you should be asking yourself. Before you start shopping for random bits of gear and/or asking the internet for creative suggestions.
> I'm aware of the various systems petzl offers etc but was hoping that someone on ukc would have a novel idea / combination of products that they use themselves.
But speaking of shopping for gear, you won't find an industrial fall-arrest lanyard made with a dynamic rope because that's what the shock absorber is for. (Also, even with good edge protection, you're unlikely to find anyone with much sense committing themselves to a textile rope or sling loaded over a sharp steel edge.)