Thanks Tim,
  Some good info it, has given me some +/- points
  +) Running costs will be reduced from £300 to £140 a year ( This is resin + 
       filters) 
   -) Will have to buy R/O system, cost around £250 would take a year to recover
       costs from savings above.
   -) Filling time is longer, with R/O system 250l would take 4hrs+, DI only takes
       15 mins
   -) Waste from R/O system
        
   Can anyone help on another question please, if I put a booster pump in
   front of the R/O would this speed up the filling time. My pressure from my tap
   is high so would this make a difference.
   
   My TDS is 40 from the tap.
  Cheers
  Doug