Checked the water coming through my Raceglaze tonight and found that it's back up to about the TDS reading is back up to 290ppm. I had noticed a few more water spots appearing recently, but that's pretty much what it is without filtration. Guess a combination of too much washing and the exceptionally hard water in my area have done for it...bought it in May last year, so not quite a full year.
Any advice of where best to buy replacement resin? It's £45 for 7 litres from Raceglaze, but I'm guessing it's a generic resin which might be cheaper elsewhere.