Thanks for all your replies.
@happymarion - how lovely. Sounds like you have the perfect butterfly- and ladybird-friendly garden.
@oldchippy - the nettle bucket isn't in the flat! The smell isn't that bad, really. I can guarantee you won't notice it if you come to paint it ;)
@kevc - dung flies are important predators of other flies, including mosquitoes, and rat-tailed maggots turn into hoverflies, which pollinate flowers and fruit and veg crops. But why do they need a purpose? What purpose do humans have? Regarding your clay soil, if you give it a really good dig over, then dig in some horticultural grit, you should notice a difference immediately. Then, every spring and autumn, apply a mulch of home-made compost/well-rotted manure. This should make the ground more manageable.
@kaycurtis - the smell isn't so bad, really, and you soon get used to it. It's fun!
Kate