Ok, so at the moment I'm thinking no chemicals - which will be in line with the garden more generally - get some water cress and then give it some time, removing the weed manually.
I didn't realise the toadpoles would become carnivorous before they left the water! There's no sign of any back legs yet, but reading up on them suggests that they should be emerging in the next month or so - and will be looking for winter lodgings around October time - so they need to get a move on!
So, water cress and dried blood worm - a shopping list that should get my husband worried
Cheers
Ellkebe