A friend of mine imports Harris sausages for Cold Storage etc, you can call him direct on 96665374 to purchase by the box. He no longer imports pork pies or scotch eggs, as these are not allowed in now. There are a couple of other choices for sausages, the Swiss Butchery in Greenwood Avenue sells a good selection, the German Bakery on Upper East Coast Road at Siglap has good German bockwurst, etc.
For good cheese try the Cellar Door or Culina on Bukit Timah road for English or French cheeses, the Swiss Butcher has a good range of Swiss/German cheeses. Finally of course Cold Storage in Sixth Avenue stocks a reasonable range. The only real disappointment is Carrefour where the cheese and sausage selection is pathetic for a French store.
P.S. I suggest you print this off, as none of the outlets mentioned advertise on the board this post is likely to disappear fairly quickly!