Dinan has no customs facility so you have to go somewhere else first. Where that might be depends entirely on why you are going!
As the previous poster says Dinard used to be great but Ryanair's demands stuffed that, Nonetheless, the town's nice....
St Brieuc aerodrome is OK for arrival etc but the town? Don't bother, soulless and split by a busy road and no charm.
Nicest place? Dinan and perhaps go via Cherbourg for customs.....
rgsaero