I think you have to be careful when quoting gutter clearing, especially with downpipes as Tom has said.
If a downpipe has a 'foot' on the end then you can hear if the pipe is clear as has been said. We sometimes are able to release the top bends to clear the pipe at the top with a bit of gentle persuasion, but we need to use ladders for this.
Some downpipes go into 'sealed' drains. We have one house where there is an inspection cover next to the down pipe so we can remove dirt in the U Bend.
We also have one where the downpipes go into a sealed housing. The downpipe has to be removed. Unfortunately, we don't offer that service and they need to get a plumber or roofer in to do that job.