MyBuilder, Rated People, etc- a lot of trust worthy tradesmen but also a lot of thieving scumbags. My GF used a "builder" she found on Rated People. She gave him £2800 for materials... and never saw him again.
She contacted rated people- they didn't seem to care but did block his profile. We later discovered that he is regularly blocked by Rated People but just sets up a new account.
It seems that Rated people allow tradesmen to delete negative feedback.
Prior to that my GF had used Rated People to find a decorator to repaint our hallway. I am a profession decorator who tries to provide a high quality of finish.
She decided that I was too busy (to do it soon enough) and that given that I had previously painted it any old decorator would be able to do a decent job.
A "five star" rated decorator, charged her £750 to emulsion the walls and ceilings, and paint the skirtings, stair strings and architraves.
It is a small hallway, 1.5m long upstairs and 3m downstairs.
The day he finished, she paid him and when I got in from work, she asked me to repaint it. Sanding back his heavy brush strokes and gritty rolling resulted in the job taking me twice as long as it would have if he had never touched it. The guy didn't even own a dust extractor or electric sanders. His tools would have cost about £100. I used about 2 grands worth of tools to sand things back without plumes of dust. I suspect that he normally does contract work, eg office blocks where no one cares about the quality of finish and all you need is a roller, brush and sandpaper.
I think that people leaving reviews public often worrying about upsetting the "nice tradesman" that worked for them, either that or they can't tell the difference between adequate and good work.
Asking friends or neighbours is often the best option, you will be able to see the work and judge for yourself.
I recently employed a decorator who drinks in my local pub to help me when I was busy. After a day I realised that he couldn't provide the same level of finish on the woodwork that I could. In the end I just let him do the masonry work. He is a nice bloke and both trustworthy and reliable but I wince when other people in the pub tell me how good his quality of finish is.
In the event that you are new to the area and don't know anyone, yes the local facebook group makes sense.