It seems these are based on the fact that the virus might remain viable for 50 days on the ground, and there are internal movements of wild birds within the country, so the powers that be have decided there will be further restrictions for another 2 months.
This is despite the fact that the infected birds themselves are moving north and east to their summer breeding grounds in the Arctic, there has been no contiguous infections from the locations like Slimbridge where infected birds have been found, and there have been no new incidences in the western seaboard of mainland Europe for several weeks.
Edit – a few hours after writing this there is another incident involving 35 birds at a farm near Haltwhistle in Northumberland
A separate conversation brought up the suggestion that letting birds out now (and culling as any infection appeared, as we have done in the past) would at least allow us to KNOW where the virus is, if it is in the ground, rather than allowing it to become endemic in the wild bird population.
So … I give you all the official links I have so far found/received, and the information, for you to each assess and interpret as you will.
My understanding is that many people will be letting their birds out, keeping feed and water inside, washing their boots, putting up some bird scarers, and feeding wild birds elsewhere; it will remain to be seen if this is sufficient.