Well, what an interesting day! I've decided to stick with the FT01 for a bit longer, but thought about looking on google to find a way to remove the top filter!
Well it's a pretty easy job, there are 2 screws on small brackets that stick out, that go vertically into the top of the case, if you unscrew those, you can slide the whole fan and assembly out (to the right, when the left side panel is off), you can then easily clean the whole fan unit and filter! Takes less than 5 minutes.
Interestingly, in my research I came across someone who did this, but then reversed the fan so it acts as an exhaust and claimed it lowered his case (core and gpu) temps by a great deal. Thought I'd also give it a go, and wow, my core temps under prime 95 have reduced by about 10 degrees C!
Highly recommend you give this a go.
I've also turned off my rear exhaust fan, so now my case is quieter and cooler. RESULT!
Here's a photo of the removed top fan and filter is off to be washed!

Woot!
You can see the two screw point brackets sticking up from the fan case in the photo, on the edge of the case closest to the bottom of the photo.