Photo editing on a 13" screen? You're gonna be doing a lot of zooming in and out.
If you are not taking the Macbook with you out and about, consider building yourself a PC if you're going to drop at least £900 (cheapest MBP on Apples site)? You can build yourself a complete rig that out performs the MBP in all ways, apart from looks. I'm talking a complete system, all the components, case, drives, including monitor, keyboard, mouse etc. You can also play some games if you're into that.