We have two lemon trees indoors by the bi-folds.

They are doing well apart from the aphids.

From recent Googling the biological controls are not available yet this
year.

Spraying advice doesn't seem to include Citrus in the UK.

Any recommendations?
More importantly, anything NOT to use?

They can be considered ornamental at the moment because they are showing
no sign of flowering.

Cheers

Dave R