Thanks so much for the help stephenw10 & wallabybob! Really did help answer a lot of my questions!
The good news is…. I managed to get it all working, only as a test run though.... I allowed the WAN IP to be set by my BTHH's DHCP to 192.168.1.102, and as you both suggested I run the LAN on a different subnet, I put the LAN on 10.0.0.1, and enabled DHCP on the LAN interface, maybe when I choose to run it full time I will set the WAN to class A and LAN to class C, not the other way around ;)
I did Ipconfig and it came back saying I got the IP 10.0.0.10 which is the start of the DHCP rule, so that shows that DHCP is working, which is great!
I'm waiting on a new modem to come though the post, I've read on this forum in posts that its one that will work with a ADSL2 line and support the BT PPPOA authentication aswell as PPPOA bridging!
So hopefully, when its all going as it should, I hope to have my WAN IP as my Public IP, and my LAN IP set to class C.
As stephenw10 suggested, having double NAT could be a pain. Especially because I do allot of port forwarding, so thats why I want the WAN to be set up for the Public IP, and therefore I dont have to run the awful BT Home Hub! ;)
The only thing I'm left to now is to learn how to use all the great features that PFsense has to offer!
I know forums are made for questions and support, but I really do appreciate both of your help.
Many Thanks,
Josh.