anyone spoken to Grohe Dal about this?

Thanks to the previous contributors for diagnostic guidance. Just installed the cistern in an awkward spot thinking it was up to the task - tested fine - 2 weeks later: constant trickle. I reckon it's alot of money for something which should be trouble free but isn't, especially if it turns out to be the blistered washer.

It seems quite a few have experienced similar problems so before I don my Viking helmet and challenge Grohe Dal, has anyone spoken to them about this?