I just did the test on the Zen internal one and the Thinkbroadband one, both tests show pretty much the same issue for me - slow single threaded downloads.

Edited by Deft (Sat 18-Jun-16 11:16:46)

A known problem affecting "thousands of people across the UK". Apparently it's not Zen specific, but haven't noticed mention of it elsewhere on here.

I logged a support ticket just so they have a report of it. Seems an ongoing problem based on the other mega thread.
I do wonder whether customers at Zen are more discerning than others, so notice network issues more readily.