Alrite Col, shame about the water meter bud. Have you not got any family or friends who aren't on a meter bud? if they can and have the space you could buy a cheap pre-fab shed and it'll pay for itself in 8-12 months.
Out of interest, what's your TDS in the pool?
If you were to go DI only, I'd deffo go twin DI setup. I ran this way for 5yrs but when it got to £100 per month in resin I had to look at other methods. I now have a merlin.
To answer your op, I recon your looking at around the £100 mark.
Finally bud, there's newer ways of preserving your membranes with the gardiners all in 1 pre filter.
I've been running 10" 10 micron before the merlin and you'd be amazed the amount of orange(rust) crap that this takes out.
Giz a buz anytime mate if you need a bit of a heads-up.
Simon
