HTC sent courier to pick up the phone last Tuesday 29th. Phone came back today (5th). They told me 7 working days and it's been 6 calendar days. Impressive service by HTC to be fair.
Dust gone so we'll see how long for. Fingers crossed.
It does seem like they've added a tiny border around the screen between the edge of the glass and the bezel. Any idea if that's my imagination?
Incidentally, after a long argument with Vodafone over the phone to their call centre they called a few days ago to offer me an exchange! Phone was with HTC at the time! But at least hopefully now a repair will have fixed the issue for good.