Mizter T wrote:

I've a vague recollection of double-deckers stood in for bendy buses
on some routes after the artics had been withdrawn after a number of
them infamously caught fire ...

Yes, that's right.

For example, Stagecoach used its own Tridents (I think from Hull if
memory serves) on the 453, so in full white-based livery (and the world
didn't end because they used non-red buses, but that's another story
entirely ).

(And the 293 - that's not an artic - is it a Citaro then?)

The 293 at the time was operated by Epsom Coaches with conventional
Citaro single deckers. It isn't anymore.

I'm half-curious to know whether the 36 and 53 were extended to cover
the extra stretches normally covered by the missing bendies (that's
New Cross to Lewisham for the 436, and Whitehall/Horse Guards to
Marylebone for the 453). Maybe other routes were left to take the
strain (though no other route from Whitehall or Trafalgar Square
exactly replicates the 453).

There were no service changes during the bendy-off-the-road saga. Most
routes eventually had something, even if was ridiculous things like
recently-withdrawn single door Darts trying to run limited Red Arrow
services.