My tree is indeed indoors - unfortunately it can't be kept outdoors at the
moment as I live in a flat (with a very narrow windowsill!).

Under the circumstances, I would suggest you bring the tree back where you
bought it & get something more suitable for your conditions, like a Ficus.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)