Apple is helped by being one of the most powerful multinational companies since the East India Company with more money and lawyers than most governments, and afaik not having any data in a UK jurisdiction.
I think that your looking at the average plod/judge and not a crowd of IT Professionals. As far as plod/courts is concerned i'd be quite concerned that they'd consider "the data is on your server" to be reasonable grounds for giving you an order to produce the keys. Ok, so you say the data belongs to "Tardigrade". They say "well, we don't have the key either".
I suppose it depends on how confident you are that the courts are going to say "oh, never mind then" to that response rather than jailing you because you haven't provided it? I think that you are a lot more confident in how tech savvy and reasonable the courts are than I am.
I'd say there is something like a 50% chance that they'd jail me. I think you think it's what, a 20% chance?
I see things in this light:-
1) Getting jailed for 2-5 years by tech phobic police and judges.
2) Losing your job since employers aren't obliged to continue employing me if i'm in prison, and after a replacement is in place for 2-5 years would my current employer be willing to fire the replacement to give me my old job back that i'd no longer know how to do because in 2-5 years significant changes will have occurred that I won't understand?
3) Getting a criminal record that will show when any employer does a criminal records check running the risk of making you unemployable.
~£5 a month
Now would you personally be willing to assume that risk for that reward? Personally, I don't think it's rationally worthwhile in the UK. Your view of course may differ and i'm happy to agree to disagree. :)