You can't go wrong with Safale S-04. I've used it many times. It's an excellent yeast and should be perfect for your stout. It was originally a Whitbread strain and the same as Wyeast 1099. My personal favorite, White labs WLP007, is a different Whitbread strain and attenuates more to produce a dryer beer.
It was a sad day when Whitbread stopped brewing after 260 years. My favorite beer of theirs was Mackeson. My father used to drink a bottle every day with his dinner. InBev still sell cans filled with a thin, metalic tasting black liquid they call Mackeson but it's nothing like the original so I never buy it. I have great memories of Whitbread because I left school at 15, moved to London and started drinking in a pub at the end of my street that served Trophy Bitter at 17p a pint (yes, I'm that old). A lot of pubs are closing nowadays which is sad but hardly suprising. I went into a small pub in Cheltenham last year where they wanted £4.99 for a pint of ordinary draught IPA. I told the barman to shove it up his arse and walked out. A lot of people must have done the same because it's now a pizza restaraunt.
Anyway, getting back to the subject, I don't bother doing a mash out unless I've got a thick mash or a recipe that includes more than 15% rye or 25% wheat or oats. It stops all enzyme action and makes the grain bed more fluid by raising the temperature. It's a bit like heating up oil to make it thinner and easier to pour.
If you ever need to expand your range of ingredients I can thoroughly recommend The Malt Miller. His range is one of the best in Europe. I find his mail order service very easy to use and I always get a fast service at a reasonable price. All of his grains are freshly milled to order and they are always the best quality. Before anybody asks, I have no connection and my recommendation is based purely on my own experience.
