Ugh... if you all are so hard-set on making this Boring, then why are we even worried about bothering getting a full-sized ship?

Urgrugg is fully capable of punching a hole into the warp. He's done it once already, and given even a little time, especially with help from another psyker, he could do it again on a bigger scale.

We don't need a warp drive ship. We can just do what the ship Urgrugg flew in on to get to the hulk to begin with did. It's stated in his CS that Urgrugg can navigate through the warp. As it's how he got there to begin with, it's completely within reason he'd think to do it again to leave. Chaos psykers, such as the word bearers and the thousand sons, can use psychic runes and glyphs to protect their ship from the harmful effects of the warp, so we don't need a gellar field. 

So, again, if you all want to be Boring, then fine... we can just hijack a thunderhawk, kill some random space marines, then get out of dodge.