Yes, you can buy a wasp nest destroying aerosol - buy one that contains bendiocarb.
Follow the instructions exactly and use it at dusk when the wasps will be in the nest. I suggest you use a face mask, or tie a damp towel across your nose and mouth.
Make sure you can get out of the loft quickly and close the hatch immediately. Don't wait to see what happens. As an added precaution you may want to tape any gaps up between the hatch and surround.
But if you never use your roof space and the wasps are not causing a problem, I would leave well alone. The wasps will die in the autumn, the queens will fly away and the nest will not be reused.
It might be a good idea to see how they are getting in and seal the entrance either after using the destroyer or later in the year when the nest is empty.