I hoping I'm not duplicating any information already posted here but the solution is simple - It hurt my head trying to work it out/looking everywhere for an answer. So I hope this helps someone.
1. Get the video you want to use in iMovie for iPad/iPhone.
2. Take the clips you want to edit on the iPad and make sure they are .mp4 (this works best I have found) (Optional) If they are short clips I edit them into one using normal iMovie and export that.
3. Use MPEG Streamclip (free app search google) to covert said files into .mp4 if they are anything else.
Drag and drop these outputted videos into a folder stored in your pictures folder on your computer.
Go to iTunes and sync the pictures folder containing the videos (make sure you have checked the sync videos box on the pictures tab)
And away you go. The videos will appear in iMovie for iPad/iPhone.
Again I hope I didn't miss this answer somewhere else and that this information is useful to someone.
Kind rregards,
Mark