Most gutter blockages are moss, leaf litter and roof grit that has compacted into a dam, and most of them can be cleared without leaving the ground. The reason to take the ground based route seriously is not fussiness. Falls from height are the largest single cause of fatal injury in British workplaces, and domestic gutter clearing puts untrained people on ladders more than any other household job.
Clearing gutters from the ground: what works
A gutter vacuum with a telescopic pole and an inspection camera will clear most domestic gutters and lets you see the result. Hooked pole attachments work on lighter debris. A pressure washer on a pole is effective on moss and is also very good at driving water behind fascia boards and under the roof felt, so it is the tool to use carefully and at low pressure if at all. None of these needs you to leave the ground, which is the entire argument for them.
If you are going up anyway
Use a ladder stay or standoff so the ladder bears on the wall or the roof rather than on the gutter, because a plastic gutter will not carry a ladder and the bracket will go. Have someone foot it. Work within arm's reach and move the ladder rather than leaning, which is the movement that causes most falls. On anything above single storey, or on soft or sloping ground, a tower is the right answer and hiring one for a day is cheap next to the alternative.
Gutter blockage removal in downpipes and gulleys
A clear gutter that drains into a blocked downpipe still overflows, and the blockage is usually at the shoe at the bottom or at the swan neck at the top. Rodding from the bottom, or dismantling the shoe, clears most of them. Below that sits the gulley, which silts up and is often the real problem on an older property. That is drainage rather than roofing, and Approved Document H is where the rainwater drainage expectations sit.
When cleaning guttering is not the answer
If water overflows at the same point after a clean, the gutter is not blocked, it is wrong: a dropped bracket, a fall running the wrong way, a split joint, or a run that was never long enough for the roof area above it. If the overflow is at the back edge and runs down the fascia, the gutter may be set too low against the tile line. Those are repairs, and no amount of clearing will change them.
Fascia and gutter cleaning, and soffit and gutter cleaning: the washing job
Clearing a gutter and washing the outside of it are two different jobs, and the second is usually quoted separately. Clearing means taking debris out of the run so water reaches the downpipe. Washing means cleaning the visible faces of the gutter, the fascia board under it and the soffit behind, which is a cosmetic job done with a brush and a detergent from a pole or a tower. Firms that advertise fascia and soffit cleaning are selling the washing, so if what you want is a gutter that drains, say so, and ask whether the downpipes are included, because a cleaned face over a blocked pipe still overflows.
Questions people ask about cleaning gutters
How often should I have gutters cleaned?
Annually for most houses, in autumn after leaf fall, and twice a year where trees overhang. Moss shedding from an old roof can fill a gutter faster than leaves do.
Can I use a pressure washer on gutters?
You can, and at high pressure it drives water under the roof covering and behind fascia boards. Low pressure, from the right angle, and never up under the tiles. Many professionals avoid it on domestic roofs for this reason.
Are gutter guards worth fitting?
They reduce leaf ingress and they do not end maintenance, because fine grit and moss still get through and some designs trap debris on top where it is harder to remove. They suit houses under trees and they are not a substitute for looking.
What is the best way to clean gutters safely myself?
From the ground, with a pole system, on a single storey. Above that, hire a tower or pay someone with one. The HSE's ladder guidance is short and worth reading before you decide the ladder will be fine.