Hi.... well like the original poster, we too had a massive ant problem. Black ones, red ones, you name it.... literally dozens of nests.
Now we didn't have a problem when we moved in about 12 years ago. But we did have a mole problem..!! Initially i thought "awww, how cute, we got a mole..... we've made it to the country life..." how wrong i was...!!!!
Anyway, long story short etc, i eventually caught the little blighter... by hand..!! yes by hand.... you have to trust me on this one, but its true.
But i'm convinced that was the start of our ant problem. As in there were now LOTS of mole runs now unused. And i'm convinced the ants made there way along these now disused 'tunnels' and set up home all over the place.
Like you and the others, i tried all sorts. Boiling water, powders, even clove oil (i'd read about it on t'internet somewhere)
Finally enough was enough. I was in my man cave one Sunday afternoon listening to the weekly gardening spot (not that i give a hoot about gardening, don't mind cutting the grass, but i don't 'do' dirt...!!), and a question came up about ants in the lawn etc. The expert geez they had on said the only sure fire way of getting rid of them was to use nematodes. My ears pricked up..! After listening to the rest of the article i came indoors and googled nematodes.
Here you go....
https://www.nematodesdirect.co.uk/9-no-ants-nematodes
Now, having a fairly large lawn, i went round and poked a cane in each and every ant 'disturbance' i could find (this was great wonderment to the neighbours kids) then counted the sticks. Hmmmmm more than 50..!! I opted to go for the 12 week, 50 ant nest pack....
https://www.nematodesdirect.co.uk/no-an ... large.html
Yes, its expensive, and you have to follow the instructions EXACTLY..!! but it WORKS..!!
Don't buy more than you need as it doesn't 'keep'.... its a living culture that irritates the ants making them move on to a new home (the neighbour hopefully). And don't move the sticks until the treatment is over.... i opted for the 12 week course, so had to carefully remove and replace each individual stick as i mowed over the areas.
I had my work colleagues smirking and laughing when i told them what i was up to.... but hey, now all i've got is the occasional small 'nest' and nothing like the 'cant even sit in a chair on the lawn anymore' problem like we did before.
Hope this helps.
Nick
Oh.... edit..... my missus also had a MASSIVE problem with ants in one of her compost bins too. So we got some of these...
http://www.diy.com/departments/home-def ... 463_BQ.prd
placed just 1 (there's 2 in a pack) next to the bin, and within 48 hours.... gone..!! all presumed dead.