well you can get smaller bottles of it too! any wholefoody/eco-supermarkety type place near you would be fairly likely to stock it, I think. Buy a 1-ltr to try, and order a big one if you want to embrace the Clear Spring way of life. Yes, I find it very effective (in my Miele ).
I use Ecover ones and have no problems with them at all. Have 8 year old dishwasher too. However, Co-op have recently brought out an own brand eco friendly tablet. I have used these too and been happy with them.
i use the ecover ones and they are fine, without even any rinsing or scraping required - in fact my MIL told me they came top in one of those blind tests in a magazine. Was just thinking that maybe its your dishwasher or something wrong with it?! But prob not... hope you find a good replacement