I came over to 02 from Zen. Because I have o2 mobile phone I get o2 landline broadband for £7.50 a month. (A saving of £10 a month) They supply a wireless router. (Some people dont like the supplied router but you can use your own) The transfer was done online, they text me at every step of the way and my speeds increased because my exchange is LLU. I have had a totally stable connection and can recommend them without hesitation.
I got a new e-mail address. Can't comment on how you would retain your current address. Perhaps someone else can offer advice on this one.
I do not work for o2.