I see the interactive map is back:
http://www.forestry.gov.uk/autumn-colour-mapI've just been up through mid Wales to the north and back again and it is moving fast. However, it's all down to species, which, where and when. It seems clear that horse chestnuts go early, oaks are starting, and beeches have yet to turn. There are long tranches of gold amid huge swathes of green, but the only place I stopped to shoot any trees at all was in the Tesco car park at Llandudno Junction because that's the only place the sun came out !!
I've read that the Wye Valley has a lot of oak, followed by hazel, birch and beech. Between the 29th and the 5th I'd say we're going to be lucky only if the weather is fine, and the forecast does not look too great for the 29th. Treewise it may only be a difference between more still turning or more leaves on the ground. Either way we'd find patches that are good, I'm sure, but without light we'd be a bit stuffed.
Personally, I'd stick with the 5th.