The almshouses were founded as the Hospital Of The Holy Trinity in 1596 by John Whitgift, the Archbishop of Canterbury, after whom Croydon's shopping centre is named. It is hard to believe now, but Croydon was the summer residence for Archbishops for until the mid 18th Century; their former residence is now part of Old Palace School. Members of the Church of England, who are over 60 and "of modest circumstances" can apply to live in the almshouses; I guess I'll need to work on the first two criteria!
The color of the door looks modern, as well as the way everything has been painted over with the same color.