Delphiniums are an absolute delight in a cottage garden and can also look amazing when planted more formally. I love delphiniums - they can be so stately and create a huge impact! I have grown them in every garden I've ever cultivated.
Slugs absolutely love these plants! There's no avoiding this issue and it can be a real problem. There are lots of ways to deal with slugs (most only partially work). I have found beer traps, nematodes, a pair of scissors and sand around the base of plants to be fairly effective. I have used copper rings aswell with some success!!
In addition, most delphiniums will benefit from staking. I tend to put four stakes in a square and then use strong to weave around to create a strong support. Don't tie too tight- you don't want the plants to snap in the wind!