The best way to eliminate Wandering Dew is to shift houses and check carefully before you buy a new one! If that all seems a bit drastic the next best thing would be to start again. I would suggest creating a raised garden in the same area. Build up the sides using railway sleepers and put a weed mat over the weeds, then fill the garden with new soil, compost and some pea straw. Alternatively, you could use Amitrol on the soil, but you can’t use it near any veges, and use a steel rake to break up the weed. Sorry I can’t provide an easier solution, but Wandering Jew is extremely invasive and hardy.