I lived in London for over 10 years and there is no way I ever hit 20% on travel (well maybe if you include holidays), let alone travel to work.
Now I live in a smaller more centralised city and it’s a fairly easy cycle. I’ve spent about £200 on bit repairs and servicing in 5 years. I’ve always made a vaguely conscious effort to live a reasonably cycle-able distance to work though. I apreciate that is harder for lots of people.
I’d estimate that I probably overshoot 2% on phone and internet etc though, which I wouldn’t have in London which has better network coverage so the cheaper options work just as well as the “premium” ones.