Yep, mine was 3.5+ hours daily for a number of years - train + 2 tubes each way, 5 (occasionally 6) days a week - hybrid working + the Elizabeth Line have been transformational for me and so many others.
I have a lot of friends/colleagues who topped 4 hours daily, and not necessarily in return for a substantial salary, more about affordability of housing and very slow trains!
Long commutes are/were also tolerated in return for living in a nicer, more rural area, better schools, cleaner air etc
Yes, good point about the tubes - and of course getting to and from the origin station - so it would be more like a five or six hour commute into a London office via Waterloo from Westbury, Trowbridge, and B-o-A.
Mark A knows a lot more about the specifics of those through services than either of us, perhaps he can jog our memories as to how often and at what times they operated? I seem to remember there being more of them on a Saturday, which might tell us all we need to know.