I can't comment from personal experience but check out their message board click here
Re- the providing your own email address thing, you can always sign up for a Hotmail or similar account and either configure it to be downloaded by Outlook or OE. Or you could sign up for a pay as you go ISP (which could always come in as a backup)and get a free email address which again could be configured with OE etc. Other than that, you could sign up for email services from something like this click here which is independant of your ISP.
If an ISP's service is working to it's maximum potential, you shouldn't notice a difference in speed between providers but I would do a bit of research click here and click here= before you make your choice. What suits one person, may not suit you.
The names that consistantly come up as "best" are Pipex, PlusNet, Elipse, Zen and Nildram.
Finally, if you are concerned about getting stuck in a contract with an unsatisfactory service, I would advise you look for a provider with a short period contract, they start from a minimum of 1 month. Use the links I provided to do a search for such suppliers.