Accessing ethernet Arduino on LAN from internet?

Yes, I'm using no-ip.com (thanks Headroom), the dynamic update client works well allowing me to SSH into my home PC & generate Telnet originated ARP requests from the internet. Though I'm not sure of the distinction I have tried both Telnet port forwarding options in my BT Homehub2 - 'Telnet Server' & 'Virtual Terminal Server (TELNET)' .

My router requires nonstatic IP address' for DMZ but allways makes the Ethernet-Arduino IP address static after portforwarding - not sure if I can override that?

Is DCHP going to offer any advantages? Using DCHP the Ethernet-Arduino reported a different MAC address 'de:ad be:ef fe:ed', so I guess thats configurable?

My ISP in my area of the UK is due an imminent broadband speed increase in a service called 'BT Infinity'. This requires a different router - just wondering if any UK users know if a new IPS/'commercial alternative' router would solve my problem? Thanks again folks - Alex.