I'd recommend UK2.Net so long as you don't mind paying for the call as they don't have a toll-free number. Access is easy, via an 0845 local call rate number from anywhere in the UK from any line which does not withold CLI (use 1470 in front of the number otherwise). No registration is require, no user ID or password (use anything for both) and you can set it up from Add new connection in dial up networking without any CD-Roms or set up packages. Check out
www.uk2.net for more details.
You can use their SMTP server for sending mail (details on the site) and obviously can pick up any email from POP servers or your Exchange server.
And no, I don't work for them or get commission! I just use this service from time to time and know it works without any risks associated with installing "Free trial" disks.