You can access pop3 email on most modern mobiles now, not worth getting a blackberry anymore IMO. Depends how much you'd use it for other stuff, appointments etc.
As for networks/tariffs, really just depends how much you'll use it and who you'll call. Orange do unlimited free calls between all the phones on the account if there is more than one mobile needed - this was best for us. They also do free insurance. You need to compare data/voice costs as this will make big difference if you use it online a lot.
We've all got these ones Good for emails and supports attachments. Nokias are generally pretty easy to use and we got them free without picking a ridiculously expensive tariff.