Anyway, That doesn't matter - I've actually found some shoes online... And I've actually bought something! More on the latter later though...
Firstly, I spent a few hours searching non stop online for some shoes, that have a similar buckle and tongue style to the one in the costume. The actual buckle isn't exact, and is much squarer than the one in the picture, but I can always buy a rounder buckle to replace it.
I actually bought something for the project! Finally! And the thing I bought was some Milliput Moulding Putty, which I'll be using to make the mask, and a sculpting tool with which I'll be carving out the details. So, after all that, I've actually purchased something. 'Tis only a small step, but is still a step nonetheless towards completing this cosplay!
(I also today had a look round some charity shops for a coat, still no success, sadly - It's looking like online is going to be my best bet!)