Depends how long its been potted up - if its only been a month or so, unpot it, carefully (wearing gloves, those ants will attack), stick it in a bucket with water in it, turn the pot upside down to empty the soil out and run away for a while.

After a couple of hours, come back and see what's happening - at that point, clean the pot thoroughly, and this time, put a piece of jeycloth or something similar across the bottom, fill up with fresh compost, replant the bottlebrush (by this time, the ants should have left the rootball because of the water in the bucket) water in well, and stand the pot on something to raise it off the ground - bits of broken roof slate, pot feet, something or other. Assuming the pot is stood on paving, dust beneath with ant powder.

If its been in the pot for some months, the only recourse is to stand the pot in something large and waterproof and fill it up with water, so that the pot is flooded, and leave it for some hours, then remove and hope its got rid of them. And stand the pot on something to raise it off the ground...

Thanks Bamboo, she potted it up a couple of days ago, she had a bag of compost in her shed & used that so I have copied & pasted your advice to her, she asked me to thank you :o)) x

Ooh, now I wonder if the ants were already in the compost in her shed... she'd better check that before using any more of it! Also make sure the plant itself does not have scale insect infestation - that's too short a time for the ants to be everywhere if its only been potted up in the last few days. If the ants are on the plant, there might be scale - she needs to check backs of leaves and stems for things that shouldn't be there.

I had already asked her to check for scale, I sent her a pic of them, she said she hadn't noticed any, she is unwell at the moment, I think I need to go & have a look for her LOL as she really hasn't a clue when it comes to gardening & plants LOL.