Until relatively recently (things have improved in Scotland especially and now increasingly in English cities) it would have been illegal to do what London does anywhere else. My city really wanted a single card that works on a bus or a train anywhere in the city, they couldn't persuade anybody involved to actually do that and the cards went away without ever being actually useful.
Irish buses are like this in principle; they're branded TFI and operated by either Bus Eireann (state-owned) for non-Dublin stuff or Dublin Bus (state-owned) or GoAhead (private) for Dublin stuff. Only way to tell these days is a small notice on the door. However, you do care whether your route is Dublin Bus or GoAhead; if it's Dublin Bus it will probably merely be late, whereas if it's GoAhead it will probably be _very_ late or just cancelled. Is this not the case in London; ie are the operators all about the same in terms of level of service?
The funding for oeprating companies varies a lot, according to the chart on page 6, 3p per passenger kilometer for Thames link, 30p for Scotrail, -1.1p for west coast.
Yes, its not anything like a uniquely British problem, its widespread. Bigger projects are a lot more difficult to run, and governments are drawn to big projects.
(1) Most tourists visit largely London and its near surroundings. Public transport in (and to) London is generally much better than other parts of the country.
(2) A lot of the downsides don't manifest if you're a relatively infrequent user and you're largely travelling at off-peak times. As a UK resident who doesn't commute on the railway, this also includes me -- my experience of trains is generally good because I travel at quieter times and I don't travel so often that unreliability is a regular experience.
(3) If you ignore the costs (by not being a taxpayer or because you're less price sensitive for infrequent travel and especially for holiday travel), then you're ignoring the large part of the argument which is "this privatization had massive inefficiencies and costs".
FWIW, the UK government pays about half of the 25 billion/year cost of the "operational rail industry" (source: https://dataportal.orr.gov.uk/statistics/finance/rail-indust...). I couldn't find the equivalent stats for Portugal with a quick search, so I don't know how that compares.