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I asked the site team today and apparently this is the shit! https://www.fulcare.co.uk/product/one-shot-drain-cleaner-1ltr/ they claim it never fails.
Chaley-
As long as it does the job. If it stays in the pipes it's awful. It's also possible to get heat build up with the stronger chemicals as they react with water producing heat. That can be enough to cause a problem with plastic fittings.
Just a word of warning about the strong stuff. I do have a bottle of one shot but it's lasted 15 years so far.Something like this a great starting point for any unblocking. You can suck and blow with it making it way more versatile than a plunger. Also useful if you are dealing with pipes full of acid!!
[https://www.amazon.co.uk/Drain-Unblocker-Powerful-Blockages-Chemicals/dp/B08H5LZPBG?
Try boiling water before you try chemicals, sometimes it's a build up of soap which can be broken down by a combination of simple methods. Worth trying to get access to the trap though as mechanical removal is by far the best method.
Airhead
No - you need something caustic. Soap based stuff just produces scum that binds hair and shit together that blocks stuff up.