I'm a bit late replying to this, but ...
VFR fork tubes will fit into Firestorm sliders, using the VFR springs and cartridges. So for a low cost upgrade, Firestorm sliders, front wheel spindle and mudguard, VFR fork tubes with your Maxton internals, 4 pot Nissin calipers from a Firestorm, Fireblade or CBR6 and a suitable master cylinder.
I got my Firestorm forks cheap because they were bent, and I already had a 14mm master cylinder (off a Speed Triple iirc), so my conversion came in at about £75