Bridging O2 modem/router with D-Link router

[blueagle78]

Hi guys, I hope someone can guide me in the right direction. I've spent hours on this and I think I've done everything I could.
I've got an O2 modem wireless router TG587n. It works well but upstairs I've got very weak wireless signal. I've got a D-Link DIR-615 wireless router which I want to use as a WDS/Access point upstairs. Both TG587n and DIR-615 are connected using the LAN cable. I've flushed DIR-615 with DDRWT firmware and its working. I've run through the guide
http://www.dd-wrt.com/wiki/index.php/WDS_Linked_router_network and my DIR-615 is setup correctly. But TG587n is locked down and I'm struggling to work out how and if I can change things on it.
What can I do to bridge these two together? If needed I've got a Netgear router (an old sky router) which is not in use right now.
Thanks

 

[Monkeh]

You don't need to bridge a thing.

If they're connected with an ethernet cable, just configure it as an AP and you're done.

 

[blueagle78]

Finally, its working now. Followed this straightforward guide and its all setup correctly now.
http://coderjournal.com/2009/01/creating-a-wireless-access-point-using-dd-wrt-refresh/
My only question is, my primary router has got different SSID than my secondary one. When would a laptop, my BlackBerry or PlayBook would switch over from one SSID to another? Because when I'm downstairs I would like them to use downstairs router and when I'm upstairs would expect them to use upstairs one.