In reverse order...

> please, tell me about the added value recruiters in the UK bring anyone

Sure.

Firstly, the last 5 candidates I've placed were not looking for jobs. Each was in a role where they were slightly unhappy, but inertia was keeping them put. Having chatted to them, I was able to find them roles they enjoyed more, with a significant pay rise. You could see this as introducing liquidity to the market. A job-board would not have found them.

Secondly, of the last job ads I've posted to job-boards, fully 50% of the applicants came from a single non-European company, and the applicants had no right to work in the UK. Of the remaining 50%, almost all were totally unqualified by CV alone. Of the handful who were qualified, a very quick technical chat on the phone weeded out approximately half again. Then the ones whose salary expectations were out of line with the hiring company needed filtering out too. When you're in a position to actually hire people, you'll get a feel for how time-consuming it can be to hire a single role. When you have 5 to fill, it can become a full-time job.

Thirdly, as an immigrant to the UK (welcome!), you'll be well-acquainted with the foibles of the UK immigration system. Candidate A's wife is on a Tier II inter-company transfer visa, and he wants to get a role; does the hiring company need to be on the UK BA list or can you just hire him? What if it's a subsidiary company of a larger company that is on the UK BA list, but it doesn't have its own registration? Is the candidate worth pursuing? What if the candidate applied for ILR four weeks ago? Is it safe to make him a job offer?

Fourthly, as you point out, the UK job-board market is not centralised, and it's not a monopoly. Where should you post a Python job? LinkedIn? Monster? CV Library? Twitter? Reed? Jobsite? Facebook? Jobserve? Any number of the scammy Python-specific job-boards? As a direct employer, your media cost is £200 a pop. Filling out each form take half an hour. Each of these systems has a different way to get the candidates and format them. As a recruiter, however, I'm using a multi-poster, and I'm paying ~£10 for the media cost, and I have the time and motivation to post the job to a wide-range of channels, but I also have a pretty good feel for where my return on investment will be.

Fifthly: What's a reasonable salary for a Ruby developer in London? What if you need them hired in the next four weeks, urgently? What about a contractor? You've probably got a gut feeling, but look, all the job ads show a range, and not an actual salary. How much would you pay for a superstar? How much for a junior? Are you paying more or less than the competition? Two types of people have access to salary data across the industry: HR people, who aren't allowed to share it, and recruiters, who share it as part of their value-add.

There are sixthly, seventhly, eighthly and ninthly here, but who reads long comments anyway?

> Russian recruitment industry as an example of smoothly-
> functioning market ... through two of the largest
> websites

So, to summarize, the Russian way is better because there is a duopoly in the job-board market, rather than meaningful competition. I can't tell if you're making a very clever ironic comment on economic centralization and its effects on the Russian economy, or you're just not thinking through the implications of what you write...

> that people like you (yes, you) will lose their jobs and
> suffer

You should consider re-reading the HN guidelines.