Usually English beers would be racked to the cask a few points above final gravity, and then conditioned at cellar temperatures - around 55-65F. Obviously this needs you to know the final gravity in advance, but you can prime to add a couple of points of gravity worth of fermentables back if you let fermentation complete. Conditioning it much warmer than this will result in too low a carbonation (19C is probably too warm), as the cask shouldn't be holding enough pressure to achieve the same CO2 volume at that temperature (if your pin does hold pressure, then you can condition warmer). As long as you didn't cold crash or leave it a long time after fermentation completed before racking to the cask, then the yeast should be able to condition the beer at cellar temps. Just above 60F should be fine with most English yeasts, particularly WLP002/1968 which ferments quite happily at 62-66F.
See the latter part of this article