Hi all,
Anglian Water isn't very forthcoming about their water quality, but I did find this <
http://waterquality.anglianwater.com/report.aspx>, by claiming that my postcode was MK10 9EN, you should be able to get the results for your actual water with your postcode.
Your water water is pretty hard, about 16.5 dH, so the TDS meter is probably mainly measuring calcium carbonate rather than anything more harmful, it does say the average value for nitrate was 20ppm, although it doesn't say the range, and I'd bet it is a lot higher than that at some times of the year judging from the comments under nitrate. It also some of the water is treated with chloramine, so you'd need a water conditioner that deals with this.
Could you collect rainwater? it's cheaper than a filter or an R.O. unit.
cheers Darrel