Mizter T gurgled happily, sounding much like they
were saying:

One other (slightly cheeky) possibility, should you wish to retain the
option of travelling on the Met line, is that you could cycle your
regular bike into Marylebone then leave it and lock it up there in the
safe cycle storage place, then either travel onward to C&L by Chiltern
train or alternatively by the Met line from Baker Street station which
is just around the corner (I'm not getting muddled this time, it really
is!). That would mean you wouldn't have to wait around in order to catch
a half-hourly train.

TBH, once you're at M'bone, it's rarely worth walking to Baker St
(5-10min) then catching a c.15min interval Met which'll take 15-20min
longer to get out to civilisation beyond the M25. You might as well hang
about, and get a comfy, fast train. It's different when you're travelling
with rush-hour, since the Chilterns can remind you of photos of Japanese
rush-hour trains... (although, tbf, Chiltern haven't started to employ
people to push passengers through the closing doors. Yet.)

However one thing I'm not clear on is where the cycle storage place is
at Marylebone (I've a vague picture in my head of it but that's not
helpful!). It's possible it is beyond the gateline

It definitely is - where platform 4 used to be, before they moved it half
way to Harrow.