Garden centres and supermarkets sell weed and feed products. They come under different names such as Evergreen and many others too but they all do much the same job. Some are granules that you sprinkle on and some you water in with a watering can. Choose the one you prefer.

Welcome to GoY Arsenal (I know that name from somewhere! lol). As regards daisies and dandelions in the lawn - I just keep on digging them up!

Lawn Weed and Feed, with or without mosskiller, as Inverglen suggests. However, if you're in the south, and suffering a hosepipe ban, make sure you do it when you know rain will fall in the next 72 hours if you use a granular one. If it doesn't rain within 4 days, you have to water the whole lawn thoroughly yourself. And it should be applied on a fine day, when the blades of grass are dry, not less than 3 days after its last cut.