2 routers 1 pipe
 

I have one feed coming into a gigabit switch.
Feeds WAN ports of 2 routers, floor 1 and floor 2. They are different companies so I don't want them to access each other.

Any advice? Any need to change the LAN settings?
My computers are also plugged into the switch with real static IPs, so I can access either router by it's static WAN IP...

Do you control the two routers? If so, then you should be okay. If not, it'd be best to stick in another router in place of the switch. That way you can firewall off the two lans from each other. I guess you've got a router upstream somewhere anyway, giving out ip addresses to the two existing routers. Maybe it's possible to directly connect the two lans to that (without the switch), and do the firewalling form there.

Everything plugs into the switch to access the pipe and has a public IP, as does each router. Remote management is set to my public IP only.

We're just having an argument over the LANS, someone is claiming that if Router1 has a 192.168.0.101 and Router2 has a 192.168.0.101 they will somehow interfere with each other, it will 'confuse' the DNS requests.
Everything I remember says they won't, they can't as they're firewalled off. The DNS will see requests from the public IP, not the LAN side.

Well having 2 routers with the same IP in the same subnet will most certainly cause some problems. Mostly likely one router will just never get used, as routes to 192.168.0.101 will always goto one of the routers. Perhaps you could just subnet the network for each of these companies, and segment the 2 logically. They wouldn't be able to access each other being on different subnets.

What routers have the same IP?
They won't bloody work at all if they have the same WAN IPs.
I dunno why I posted the question, it's obvious. LAN1 and LAN2 can't talk to each other unless I go out of my way to make them.
You can access either router by it's IP without bothering to subnet anything.

You are correct.

You can have 90 routers side-by-side with the exact same internal IP scheme, and as long as all their external IPs are differently, they'll happily pass packets all day long without issue.