I've just been to Plakias without pre-booked accommodation and got a room at Kyriakos Apartments within 5 minutes of getting off the bus. This used to be two separate places including Kyriakos leatherware shop with rooms upstairs, which now seem to have been combined under new management.
Nice ensuite twin room with shaded balcony facing the sea, fridge, kettle and reasonable selection of corckery and cultery, towels and bedlinen changed every day. Very quiet location. Rooms at the back have a great view of the hills. If you go up Nikos Souvlaki Street you'll see it on the corner, across the road from a taverna (Medousa or Menousos or something like that). I've probably got their card somewher if anyone wants a contact number.