Ants and ladybirds

Hello all, novice gardener here. I've recently moved to a house with a lovely, mature garden, so I want to look after it and am keen to start gardening There are a lot of greenfly on the roses. After one false start with some horrific bug spray (never again), I thought I might buy some ladybird larvae to sort them out. But the advice says, "do not use when ants are present" and I don't want to import ladybirds just for them to be killed! Now, I have never seen a garden with so many ants in. Everywhere I turn over the soil, there are ants. They are climbing up the wisteria, in the rose bushes, in the flower beds, in the rockery, you name it. They were in the kitchen when we arrived, but I have got rid of them from the house (sadly had to resort to chemicals). So, I don't really want to use toxins in the garden (I want to protect the bees etc), but I am stuck in a bit of a loop. How can I get rid of the ants, so I can bring in the ladybirds to get rid of the greenfly?
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i'm on the south east coast and i also have ants everywhere. I have also had greenfly/ants on my bramley apple tree and couldn't buy the ladybug larvae for the same reason as you, the ants apparently look after the greenfly as they secrete a sticky sap that the ants eat
i sprayed my apple with a washing up liquid/water solution with some chilli in which has got rid of the greenfly and killed the ants that were there when i sprayed but the ants are back up there again, my mum used to use boiling water on the exit holes of the ground where they were coming from. I know you can get like a really sticky tape to wrap around trunks but then you would have to make sure they haven't got any bridges like leaves/ walls that they can use instead 
As far as ants, a good smear of vaseline or similar is reputed to stop them climbing up the main stem. Old wives tale or not, I couldn't really say.
Try to look on the bright side - if you have that many ants you probably have green woodpeckers around - keep your ears open for their yaffle in the early mornings, and watch for them probing the lawns with their beaks to get the ant larvae
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
Thanks everyone. I am very grateful for your very patient advice
It would be lovely to have roses that aren't swarming with greenfly though so will have a go with some washing up liquid solution. 
Jimmy i tried the vaseline around the trunks and they just walked straight over it haha but they did comment on their lovely soft feet
Ah bum, ring of ant powder around the base of the offending its not organic bt it's a better option than a plant full of harvested aphids.
Yes, that is what I did when aphids were attacking my blackcurrants. The real issue was the ants. A ring of powder around the base kills ants going back and forth but does not kill bees. Water with a little squeasy in can be used to wipe out easy to see ants. As far as I know it only kills on contact, and does not persist.
Incidentally, pyrethrin, which kills ants and is closely related to ant powder, is organic. Not that you should really take too much notice, some organic chemicals are very toxic. Pyrethrin is low toxicity, but I think it can harm cats, and fish too, so check up online, and don't use if you have pets in the affected group.