I can advise you to regularly clean the area around your lemon tree to remove any food or debris that may attract ants.

Yes I am definitely going to have to do something there. I have planted some mint there in the interim... but I do think extra action is going to be necessary.

You can also use organic mulch around the base of the lemon tree to deter ants.

I was not aware that mulch was disliked by them - thanks for that tip! Bad for the ants and good for the tree - a win win!!! YAY! :)

If there are too many ants, treat with a suitable insecticide.

Bought one yesterday and the pressure pump to spray the tree... so will probably do that in the next day or so when I have a gap.

If that doesn't help, you can add natural enemies of ants to your garden, such as ladybugs, spiders or lion ants :)))

Thank you so much for the tips. I have really gotten some great advice via the comments of this post, so am really grateful to you and everyone else for sharing all your tips and knowledge :)