Hi Simon,
In my experience, the Merlin is the only RO that completely meets your specification within your budget. The makers only claim 93% rejection of TDS, compared with the more usual 95 to 98%, at a mains pressure greater than 40psi. It's in stock and on offer at the moment, click on
http://www.andwat.co.uk/acatalog/REVERSE_OSMOSIS_UNITS_.htmlIt's a superb machine,
in the right set of circumstances, which we have specially tweaked to greatly reduce the amount of water which it normally sends to waste. You'll have to be prepared though to spend more on resin for your final demin treatment, and to add an extra carbon prefilter (one off your old RO will probably do). If your mains pressure is below 40, you'll also need a booster pump.
Our RHOMBUS 3, or RHOMBUS 5 , both of which include pumps and in-line TDS meters, may also be of interest.
If you want to take matters further, PM us or ring on the no on the website, and we'll get one off to you tomorrow by courier, for delivery Tuesday.
Hope this helps,
Yours, Andrew