Just because we already have a few coffee shops in Forest Hill doesn’t mean we shouldn’t have any new ones. Aga’s, Archie Parker, Teapot and David’s all have very different vibes, and I’m sure this new coffee shop will also have its own unique contribution to the high street.
Also - the more competition amongst coffee shops, the harder they will all have to work to treat their customers well, offer them better prices and more exciting offerings. A stagnant high street can lead to laziness of existing retailers and, ultimately, their failure as consumers get bored and stop giving shops their custom.