In Germany the kind of work from your example is highly regulated. That said, if you put an ad to build a shed for £100, expect a low quality result. Of course

In Germany the kind of work from your example is highly regulated. That said, if you put an ad to build a shed for £100, expect a low quality result. Of course you can put all kinds of criteria but at some point you will either get screwed over or nobody will answer the ad. I also doubt that there are many people working on such gigs in a sustainable manner, even if the criteria are proportionate to the price.