Do I Need This Bit Of My Filter?

I have this tank http/www.aquaone.co.uk/betta-aquariums.php
Water leaves the front section through slots at the top back of the left hand section.
Behind that are two removeable filter pieces that slot in. The first is carbon covered by white wadding, the second is full of ceramic balls. The next section to the right was empty, I've used that to put media from other tanks to try and clone the filter. The next two sections have enormous pieces of black foam, then another section for the heater and lastly the pump which sends the water back through the divide into the right hand tank.
Not surprisingly, the first removeable filter piece is really dirty, I assume its job is to catch all the tiny particles? And the carbon isn't needed unless I'm removing medication, right?
Spares are, obviously, available http/aqua-one-parts.co.uk/spares-by-aquarium/aqua-one-betta-aquariums/aqua-one-betta-trio-aquarium-spares
Not at outrageous cost, but still...
Attached are pics of the removeable piece in question, with the wadding torn off a bit so you can see inside, and a shot of the back section of the tank.
When I did a water change today, I fill the front and it goes into the back section through those slots, and it was slower than normal, so I'm wondering if this part is getting gunked up and impeding water flow.
So, can I just remove this bit, will there be significant bacteria on it? (The tank's fairly new, and I don't want any spikes)
I could then move the ceramic balls bit forward. Should I just suck it up and buy new, or is there a way to perhaps chuck the carbon and fix wadding to the front with elastic bands? Is regular sewing wadding suitable, or is it special stuff in fish tanks?
Thanks for any guidance
lol, looks like someone got there before me with the laggy bands idea! http/www.ebay.co.uk/itm/AQUA-ONE-1C-REPLACEMENT-FILTERS-FOR-THE-XPRESSION-FISH-TANKS-FITS-17-21-27-32-/371054646296?pt=UK_Pet_Supplies_Fish&hash=item5664949418

I'm not certain, but I think you could exchange those filters with a sponge since you have ceramic balls in one of the compartments. The ceramic balls will have the needed beneficial bacteria although there will be bacteria on these filters as well. Making your own batting filters with elastics sounds like a good idea too! Not sure if you'd need to worry about the elastics leeching something into the water as they degrade though.

I have a HOB penguin filter.  I use elastic bands to attach 2 laters of floss and a sponge  to the plastic cartridge which has the old floss removed from it.   The elastics do eventually break from slight deterioration but I don't think it affects the fish at all.   I buy the floss in bulk for about $8 for a large roll that lassts about a year or more---saves lots of $$ compared to oem filter cartridges.   I change out one layer of floss monthly and just squeeze out the other layer and the sponge in tank water.

My AquaOne tank (620T) has a similar carbon and wadding filter insert. I have stopped buying the $20 per set filter inserts every couple of months (as recommended) and put in a sheet of filter wool instead. Apart from the cost, I was throwing out bacteria colonies and constantly forcing my tank into mini-cycles.
 
The way I see it you have two options. Replace the cartridge with a piece of foam/wool the same size (they're also easier to clean than the cartridge); or leave the cartridge in there and not worry about the carbon, after a while it's fairly ineffective, but bacteria will grow on the surfaces. I still have the smaller of the two cartridges in my filter, one day if it gets too grotty I'll replace it with some foam.