The 056/057 frames use a 34.9 mm clamp on front der and the cable comes from the top. Not sure about the size of the Goblin tube, but it is the same style front derailleur as the 056/057.
The 256 has a direct mount front, and the cable comes from below which is different from the Goblin frame. You could probably get it to work, but it is a different setup.
Looks like the Goblin also has a tapered headtube, so you should be OK there. The small 056/057 and 256 are 105 mm long, but the other sizes are longer, up to 135 mm. The Airborne page shows all Goblin sizes with a 110 mm headtube length and a couple of spacers, so as long as you didn't shorten the steer tube you should be OK.
The IP-256 drawing I got from iPlay doesn't show standover, but for the 056/057 it is 769, 805, and 826 mm or 30.3, 31.7, and 32.5 inches respectively. I would like a bit more, but I haven't smacked my nads on the top tube yet.
I have the Necco headset that IPlay sells. Some don't like it, but it works for me so far.