if you buy a self-cutting garden tap kit, you can use the kit under a kitchen sink, they are about 10 quid in B&Q etc
then just run the 6mm pipe to that, ive just moved my water rain butts this week, i have left my RO in the garage and run a 6mm pipe around the house, its about 30 M's away
you can either have the RO in a kitchen cupboard and run the 6mm pipe from that (great for the winter)
OR
run some 6mm pipe to a RO next to / under your water tank stand
its all very easy