There are many ways, but commonly used rankings are
https://www.topuniversities.com/university-rankings/world-university-rankings/2023 for international, and
https://www.thecompleteuniversityguide.co.uk/league-tables/rankings for UK-based rankings. I personally prefer international rankings to compare our unis to the world, and because the local unis uses stuff like "student satisfaction" (very subjective, and biases lower ranked unis).
For me, this is my overall perception. Some subjects are better, some subjects are worse. Some unis are at the upper end, some are at the lower end.
Tier 1 - Best: Oxbridge
Top 2 unis in UK, comparable to MIT/Harvard/Stanford, truly world-class in their unique ways.
Tier 2 - Prestigious: UCL, ICL (2+), Manchester, Edinburgh, LSE (2+), Bristol (2-), Warwick, Durham
The remaining stronger Russell Groups. Not as good as Oxbridge, but they're still great universities. International reputation not as great as Oxbridge, but their influence is definitely beyond the UK. 2+ and 2 are difficult to distinguish. Top 10 unis in UK.
Tier 3 - Decent: Glasgow, St Andrews (3+), KCL, Southampton, Leeds, Birmingham, Lancaster, Nottingham, Sheffield, Newcastle, QMUL, Bath, Cardiff (3-/4+), Royal Holloway (saved because of music), SOAS (saved because of arts) etc.
All but 0-4 Russell Groups are at this level or higher. Top 25-30 unis. Includes some which are world-class for a few subjects.
Tier 4 - Mediocre: QUB (4+/3-), Liverpool (4+/3-), Sussex, Loughborough (4+), Reading, Strathclyde, UEA, Oxford Brookes (4-), etc.
Run-of-the-mill unis, some are better than average, some are below average. Down to about top 50 UK.
Tier 5 - Poor: University of Kent and quite a few unis honestly
Prospects aren't great, not much there except maybe that odd specialist subject or two. Top 100 UK.
Tier 6 - Crappy: University of the West of England and a good few unis at this level
While not scams, the prospects are poor in most cases, unless you're lucky or in a better area than overall. Top 100-125 unis.
Tier 7 - Trash: Uni of Bedfordshire (7-), some Mickey Mouse degree-stampers
A lot of the degrees there are genuine scams. Only thing you'd be able to do is get over the degree stamp. But really, why are we funding these unis? About 6 unis here.