I'm surprised at the recommendation of Rooster potatoes. The only pack I ever bought was from LIDL and I tried to boil them to make mashed potato. The damned things completely disintegrated in the water, I'd never had a disaster like it before or since!
Perhaps I got a duff batch? 
I think you must have done, Santa (although Lidl seem to have discontinued stocking Roosters of late). Since discovering them a few years ago, my wife and I have used them in preference to virtually everything, including King Edwards by which I swore until then. Roosters really do seem to be the best yet "one potato does all", and they have an ever better flavour than KE. We roast them, boil them, mash them, make Bratkartoffeln from them, and even use them for chips if we run out of ready-made (cut into slices, parboil slices, cut into chips and flash-fry at 190C).
** Phil.