I'm with Be* which is practically the same service (they share the same dlsam at the exchange and backhaul etc) as they are part of the same group.
I dont know if O2 do this, but Be constantly kept me up to date what was happening by texting my mobile with updates such as migration date, when they had shipped the router, and when my connection was live etc.
The router arrived a couple of days before my migration due date. On migration day, I lost connection at around 08:50 and the process was completed at around 9.05 when my old router attempted to resync... but obviously wasnt able to connect to the internet.
I simply disconnected the old router, plugged in the Bebox. There was a CD that came with the router, but I didnt use it at all and configured everything myself.
Theres no point really pluggin the router in beforehand since O2/Be are rather different and dont use PPPoA like other ISPs and instead use routed ETHoA.. so leave everything until you notice your BT connection has gone off.
The only problem Ive had with Be is that some days their DNS Servers are carp (O2 share the same ones), so it may be worthwhile choosing a backup DNS server.
If you have DNS problems then you will find you get "Page cannot be displayed". We can easily help you add another DNS server once youre live.
O2 wont be able to tell you the exact time of migration since that will be down to an engineer at your exchange physically moving your line over to the Be DSLAM, which can be at any time on the given day.
