To host a website you need a webserver with all the necessary support programs. The DNS-320 in standard form will not do that.
If, on the other hand, you just want to serve files then the built-in FTP server will do that with ease. To be able to access the FTP server from outside your internal network requires setting up your gateway router/modem correctly - opening the correct ports and making sure they are forwarded correctly as well as making sure the firewall settings will allow it. I'm not sure that the BT home hub will allow you to do all that - a friend in the UK had to use another router/modem to allow her to do that.