For shanty towns, you only need to go to Paris, where I could point you at a number. There aren't any here, only because the authorities are so strict in removing people from unwanted locations, which hides the problem to a certain extent.
Walk round Westminster at night, and you'll see quite a number of people in sleeping bags resting on pieces of cardboard. They all move on every morning, with or without persuasion from the police and the owners of the doorways. These are the ones that the homelessness charities can't or won't help. Similarly, Birmingham, Manchester.....
Go to Temple underground station every night, and watch the mobile soup kitchen dispensing food and sympathy to hundreds. (Other soup kitchens are available) Then walk round Westminster during the day and look at the beggars on the street.
There are charities that have been set up to distribute unsellable (Close to its sell-by date, etc.) food from supermarkets to those in need, and others that put food boxes together for families that can afford either rent or food, but not both.