Help on connecting 2 routers

[#1]

I just had my broadband upgraded to Fibre and Plusnet sent me the new modem/router Technicolor TG582n. I have this connected to the fibre modem from Openreach and everything is working fine. However, this TG582n connects to the fibre router using one Ethernet port thus leaving me with only 3 available Ethernet ports. I have more than 3 Ethernet devices that need connection to. Luckily I have the old Thompson  TG784 with me that is lying unused.
Can I connect this to the TG582n to gain more Ethernet ports? What changes do I need to make to the TG784 to make this work? I know I need to turn off DHCP and the wireless bit. I dont think I need to put the TG582n in bridging mode since I want to use the wireless and ethernet ports off it.  Can I simply set my devices (clients) to static IPs that are in the same pool as that assigned by the TG582n and hope this will work?
Here is a diagram:
Wall connection ------ Fibre modem ------------- TG582n ---- ----------------TG784
                                                                        |                        |
                                                                        |                        |
                                                                    Wireless,            Ethernet only
                                                                          Ethernet
So my plan:
1. Turn off DHCP on 784
2. Connect ethernet cable from WAN port of 782 to port 2 of 582n
3. Use static IPs on clients connected to 784 that are in same range on 582n.
Is the above possible? What config is required on 784 to let it know that WAN port should be used to send all traffic since in a single router scenario that port is not used?

[#2]

I suggest you are making things unduly complicated by trying to use the WAN port. If you plug in to one of the TG784 ethernet ports it should just work with all the NAT etc being handled by the TG582. Of course this gives you one less port.
Alternatively, simple switches are very cheap (and easily obtained off eBay).

[#3]

Why do you need the TG582 at all ?
The TG784 has an Ethernet WAN port in addition to 4 LAN ports. Unless you have more than 4 Etherent devices then just connect the TG784 ( via its WAN port ) directly to the modem and configure its for a PPPoE connections with your PlusNet username/password. The spec for the TG784 claims that its autosenses the WAN connection type being used, not quite sure what that means in reality but I would hope it would disable the DSL port when you configure the Ethernet WAN port.