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.