My brother is in the process of moving across to TT on my advice, the main driving reason being how cheap unlimited broadband is with TT. I have also noticed they have some excellent value mobile phone packages available to TT customers. TT use the Vodafone network so coverage shouldn't be a problem and you are even allowed to use your phone for tethering with the data used simply coming out of your allowance. So he will also switch his mobile to them when his account allows - once it's fully active I presume.
I do have my reservations about TT customer service but things do appear to have improved from what I've seen on various forums recently, this may well be put to the test as his line developed problems two days after signing up, and with switch over day looming on the 2 January I doubt it will be fixed by then.
With regard to the OP's email address this is a trap a lot of people fall into, as others have said all you need to do is sign up somewhere else for an email package or even just a domain name. I use 1&1 for my domain name, which costs me about £4 a year. I simply then set up my domain name emails to forward to my ISP account, this costs nothing extra and I can have as many email addresses as I want. If I change ISP then I just need to change the forward to address, simple.