Can the filters be accessed without removing the seat?
...and how does the seat back remove to access the filters?
I have done a search but can’t seem to find any posts regarding the normal servicing of filters.

One filter is under the seat, easily accessible, on the drivers seat it under the front right hand side of seat. 2015 4.4 AB
GSXR 1000 K5
R1 1998

Following

Does this help with locations?

Click image to enlarge

This was posted by another forum member, Zeppfish I think, so the credit goes to him. But it certainly helped me.

The seat doesn't actually need to come out, I removed mine as I had no clue how to get the back off & the info I'd got from forums / peeps who'd done it themselves seemed to be inconsistent. 

(Hopefully this will help - read this as as if it were the drivers seat - but I am going from memory)... 

The seat-back leather trim that is tucked & clipped under the seat is unclipped (I re-hooked it to the seat back pocket for convenience so it didn't get in the way). Dead easy - 3 second thing. 

There's a white piece of plastic panelling on the rear lower part of the seat back -spanning across the seat, which is unclipped by pressing a tap which is on the inner side of that panel - same for both side of this panel. This is deceptively easy to get off - but don't pull it - until you've found the tab with your fingers. Then it'll come away from the side really easy. 

Once that trims is removed (I disconnected the 12v battery & waited 10 mins owing to air-bags), you may want to disconnect the seat connectors from underneath (again, just thinking about airbags? Up to you). 

I'd removed my seat-buttons trim entirely - but I don't think that's required - just the rear-ward part of that trim, nearest the seat back will need to be popped off, to allow the rear lower part of the seat-back cover to unhook - you'll probably see what I mean when your eyes are on it. 

The lower rear right corner of the seat, where the seat-back cover curls around the back of the seat essentially unhooks - outward toward the drivers door / you. There's a plastic trim around a spindle which can be removed / popped out which might make it easier - but you don't need to do that IMO. 

On the other side, rear back left corner, again - the seat-back unhooks off a spindle - trim needs to be eased aside to allow the seat-back trim to unhook off outward this time in the direction of the passenger seat / centre console. 

Then the seat back cover, should, simply (with both lower corners that were hooked over the bottom of that seat spindle I referred to - unhooked) push down and come off in your hand. You don't need a lot of pressure - remember, this is supposed to be somewhat easy - as the seat filters are a service-swappable item - so LR don't remove the seat to get at them!

Wasn't me! 2006 RR sport HSE
Swapped for 2012 4.4td v8 Westminster Santori black with Ivory leather
BEEN SMILING EVER SINCE

Found it. It was tj2k