ggplot(data) +

      geom_rect(aes(fill = recycle_rate_1718), 
                xmin = -Inf, xmax = Inf, ymin = -Inf, ymax = Inf, 
                alpha = 0.3) +
  
      # geom_line(aes(x = Year, y = Recycling_Rates, group = Area), size = 1.5, linejoin = "round", lineend = "round") +
        
      facet_geo(~ Area, grid = "london_boroughs_grid", labeller = label_wrap_gen(15)) +
      
      scale_fill_viridis_c(name = "% of household waste recycled, 2017") + 
    
      guides(fill = guide_colourbar(title.position = "top", 
                                    barwidth = 13.5, barheight = 0.5, 
                                    ticks = FALSE)) 

Source: London Datastore