It depends what your objectives are, I guess.
If your objective is to farm them and sell fat lambs, then a conventional terminal sire would give you good lambs that should be easy to sell. Charollais would be a good choice.

It will overcome any dopeyness from the Suffolk, and that combination should give a fast growing, cracking good fat lamb. Make sure you get/use a tup with plenty of wool on his head, though - you don't want the lambs to be too bare.
Otherwise a Texel, I guess, but try to get one that isn't too huge in the shoulders or rump.
Just seen your post about Zwartbles... I haven't ever used Zwartbles so I don't know how the lambs would turn out. Would they be black or white? Until you are known as a competent producer, I'd be inclined to stick with the well-known sires, and certainly to be producing white lambs if you are planning to sell in the ring.