Here in the U.S., there are two types of ground nesting bees, the solitary bee, such as the burrowing (sometimes called mining) bees and the social nesting bumble bees. Since bees tend to be the same world-wide, I suspect the species you see are similar. Both are beneficial and both are not aggressive. having said that, if surprised, cornered or aggravated (such as by a relentless cat) they may sting. The bumble bees are the largest of the ground nesters. If possible, I'd ignore them and (sounds hearltess, i know) let the cats learn a valuable lesson. If you have to eradicate them, wait until evening and use a powder version of an insectidcide such as Sevin... By the way, the bumble bee nests can be fairly large underground chambers... say 6 inches to a foot in diameter... Best of luck!