More sugar means more alcohol. One kg of DME and 1kg of sugar added to a Morgan's kit should push your ABV up into the 5.something percent range which is a bit oomphy for a Pilsener but still acceptable.
However, more refined sugar (corn sugar, table sugar, etc.) also means that the yeast might become stressed (especially due to high levels of table sugar, i.e. sucrose) and may produce off-flavours, most noticeably green-tasting acetaldehyde (green apples flavors, freshly stripped tree bark aroma's).
Also keep in mind that if the yeast has to deal with high levels of refined sugars, it may loose its ability to ferment malt sugars, which may lead to a stuck fermentation.
Having said that, once the beer is in the fermenter it's a bit late to take ingredients out of it, so I suggest you let it ferment, bottle, and see what comes out of it. You'll probably be fine. Slight off flavors can usually be removed by more bottle conditioning.