Peter
The VIIc is a nice kit to build, without major fit issues or flash.
The only thing which needs a bit attention are as mentionned the forward torpedo doors which don't seem to fit just right.
If you want to really make your sub look realistic, you can open up all the floodholes in the hull and on the deck. It's a lot of work (good excuse to finally buy that Dremel tool) but it makes a lot of difference.
There is some Pe stuff available, but in fact the kit looks superb out of the box (except for maybe the deckgun and aft machine gun which look both a bit simplistic compared to the amount of detail on the hull.
She is worth every penny  and every centimeter of space she'll need in the house...
have fun building and keep us posted on your progress. 
