NAS Drive & FTP Access to it

[#1]

I am thinking of getting a NSA drive.
I see some have ftp servers allowing you to get at your data from outside via the internet.
this would be useful at times but...
do I need a static IP address to do this?
I am sure the ip address i get from Plusnet is dynamic.
Thanks

[#2]

I have a dynamic IP but use http://www.dyndns.com/services/dns/dyndns/ to keep the IP updated to a domain name that will always point to my router, it's a free service and should work fine
Hope that helps,

[#3]

thank you for this
sounds perfect.
Thanks