13" Macbook Pro Retina - 128 or 256GB?

I'll be buying my first MacBook (the 2014 13" Pro w/ Retina Display), but I'm not sure exactly which model to get, in terms of storage space - the 128GB or the 256GB model.

I will be using the laptop for everyday internet browsing and emails, as well as iTunes and watching movies etc. - which wouldn't need all that much space. However, I'm also a photographer (so tend to use Adobe Photoshop quite frequently) and will be a Uni student in a few months time (so will use even more documents etc than I already do).

My question to you is should I just save $250, buy the 128GB model and use my external hard drive as a storage system for my films, TV shows, music and photographs; or should I bite the bullet and spend the full $1849 on the 256GB model and be able to at least store my music and my latest/favourite photographs on the macbook too (so then I have a backup on the hard drive)?

If it's any help, I have around 40GB of music, around 70GB of jpeg and raw photos, and over 300GB of films/TV shows.

Also, possible stupid question, but will my local Apple store likely (official store, not authorised reseller) have the macbook in stock? I plan on calling to check anyway.

Thanks