Well i have an answer from HTC.
Bit of a stock one most of it, but before the usual "if this doesn't work return it for a repair..." phrase, they actually admit there is a problem and are looking into it.
Exact words are:
"We understand that there are currently issues with Wi-Fi connectivity..." then later..
"..please make sure that autoupdates are enabled to receive a fix once release.."
It goes on but basically I've possibly added this to the pot. We'll have to wait and see.
Usually it's covered by "updates to improve stability" etc.