Gypsy Cob/Irish Cob/Gypsy Vanner are all the same. The last, just being a name some clever money-spinner slapped on them to sell them for big money in America. In the UK, gypsy cob refers specifically to one with a loud paint pattern, wheras Irish cob can refer to either, in general.
I know looooads of them and I think they're fab. There's no height limit really, but the average size for cobs is around 14 or 15 hands, so they're not huge unless specifically bred for it. The idea of the type is to be a weight carrier, and 'tall' doesn't often help with that, contrary to common thought.
Gypsy cobs in England have the reputation of being slow, steady and bombproof, as well as rather unathletic, but I've seen them defy all those stereotypes! They are fab, usually sensible little horses though, with bags of character.