Weeds

Hard graft, mostly! Sounds like the weeds you're having probs with are the ones with long tap-roots. You need to get rid of the root, or the weeds will keep coming back. Preferably dig them out with a spade or trowell, or if you MUST use chemicals, get a 'systemic' herbicide - these go in thro the leaves and go down into the roots and kill those too. When you say 'knotweed', what do you mean exactly? If it is Japanese Knotweed, you are probably stuck wtih it for good - the roots go down metres and are not killed by any chemical. It is also a 'notifyable' weed whcih means you are by law required to tackle it, but most people just leave well alone, because it is difficult to dispose of.