Hi Lewis,
Nice effort! I think you've actually captured more detail in the nebulosity than you realise...
I've taken the liberty of posting a quick non-linear stretch (Curves in PhotoShop) of your image. (Please let me know if you'd like me to remove it - I'll happily do so.) It'll look much better applied to the original stack.
If you compare your data to
the recent APOD, you'll find that you've captured a fair bit of the nebulosity in a short time. It only gets better!
Cheers,
Dave