Single dose poisons need a licence, but double dose (ie less effective) poisons are still available without a licence but in smaller volumes, these are generally sealed in individual 100g sachets nowadays.
The poisons should ALL still be treated with great respect and used with the professional bait boxes, weighted down and clearly marked etc to avoid any issues with non-target species still though.
I tried many things before resorting to poisons as I have cats, dogs, chickens and feed the wild birds, but in the end it was the only effective treatment and the problem was getting wildly out of control while my other ineffective efforts were trialed.