Matching varies by employer and isn't a legal requirement. The legal minimum employer contribution is just 3% if you put in 5% and it's arguable whether 8% is enough for a comfortable retirement.

For most 40% tax bracket earners (earning less than £100K) once you get beyond your employers match, there's not much benefit to a workplace pension. A £100K earner sacrificing 10% in to a workplace pension scheme is only £200/year better off than someone taking home that 10% and paying it in to a self-managed scheme (provided they reclaim the tax).

Things change dramatically over £100K. Someone earning £120K and sacrificing £20K in to an employer scheme ends up £4400/yr better off than with a self-managed scheme.