You're making me thirsty now!
Shiraz is (like Chardonnay, among whites) a grape that produces a lot of 'drinkable-but-not-special' wines and just a few really, really good ones. The Pichi Richi has gained plenty of good reviews though, so it seems that it's one of the better ones at its price level. (I suspect that the addition of Petit Verdon grapes into it might well account for that, as it means that it will be closer to a Bordeaux-style wine).
The Rosso di Puglia uses Primitivo grapes which, in my opinion, often means that the wine will be highly-quaffable (particularly when slightly softened, as here, by the inclusion of Negroamaro).
M&S wines are usually good anyway. While Asda, Tesco, Morrisons, et al all have equally good wines, you need to find out which ones they are amongst all of the 'run of the mill' stuff that they also sell. In M&S the wines are usually all of a good quality, even if they're typically a pound or two more expensive. Perhaps surprisingly, the only other national retailer that tends to only sell good wines (once you get above a certain price threshold) is the good old Co-op.