Hello Lee. Welcome to the forum!
Wow, that must be one hell of an ants nest!

I'm not really sure what to advise but I wouldn't want to spread the ants onto my plot. When we took on our allotment six years ago, it had been unworked for four years and was teeming with ants nests. We reluctantly destroyed them by digging them out, as the ants extensive tunnelling can play havoc with plant root systems. On the part where we made our brassica bed, we hadn't totally got rid of them and the Brussel Sprout plants didn't do very well and ended up as aphid farms....the ants cultivated them which resulted in sooty mould growth on the plants from the excreted honey dew. The sprouts were useless.
Ants don't like disturbance and will usually move their nests and all their eggs/grubs to a safer place, so I would think your only course of action would be to give your compost bin a good old digging, if you can access it and destroy the nest. I don't like doing this really but
needs must and all that. I do like ants...they're fascinating creatures but not when they make their nests in an inconvenient place!
Be careful you don't get covered in ants though...some of 'em can give nasty nips!
Good luck and let us know what happens.
Cheers.