Here's an update on the Porros - I tried to clean the 820 non-EDs by immersion and ruined them because although it said waterproof on the outside it didn't mean that waterproof. After a long wait and many email messages via WarehouseExpress I got a replacement pair, which were faulty on arrival - one side permanently blurred and rattling when shaken.
In the mean time I had got a pair of 820EDs because I did like the optics. On Sunday I went to the Forest of Dean and spent a few hours birdwatching in the rain. Yesterday I noticed that the 820EDs were internally fogged on one side. Putting them on top of a radiator for a few hours seems to have cleared that, but confirms that the 'waterpoof' marking on them doesn't mean waterproof in the sense of being rainproof for a decent length of time, either.
So I am accumulating multiple worries about the company, their use of english, and their quality control, but the 820 optics do seem to be good.