Can't export imovie due to lack of space

I really hope someone can help. I have created an imovie on my 16gb iphone 5 using the photo's and video's from my camera roll.

However when it comes to exporting to camera roll, I get an error stating I need to free up more space.

I am unable to do this as I have already deleted every app except the stock apps, I have removed all my email accounts, I have done everything possible and can't free up any more space.

I can't delete the photo's and video's from the camera roll otherwise imovie won't be able to export as the source files will be missing.

I exported to itunes as a project but this isn't what I wanted.

Another option I thought was to upload it to youtube, however as the imovie is longer than 15 minutes, it gives me an error, even though my youtube account allows uploads of longer than 15 minutes.

If there absolutely nothing I can do? Surely there must be a solution to this.

I have already performed the trick of editing the imovie slightly to reduce the space used by imovie, and even with around 6.7gb free it still says it doesn't have enough free space. The movie itself is around 25 minutes long.

Any help would be appreciated