It would be relatively easy to get “Recommended Contractors in London” to the top, doing as you suggest, but it wouldn’t solve the second part of the problem. i.e.
The results could be confusing to searchers, if a forum member(s) who is not a recommended guru, “innocently” or otherwise, posted within a topic or several topics, something like *“I was a decorating contractor in London and recommended such and such a product and it worked brilliantly”.
That sort of cheeky post wouldn’t be top because we wouldn’t allow duplicate titles, but if there are a bunch of generic looking results highlighting recommended contractor in London including ours, now the searcher has a potential problem - who is the recommended one and who isn’t.
Is it feasible to extend the highlight facility for search results so that the whole result for pre-determined Pillar posts was highlighted? Whenever and wherever they appeared in search results, they would stand out as trusted.