I would expect a single bridge. Can you please supply all the information how of the ISP? Where should you use VLAN’s? Only IPTV, or is it for Internet?
The WAN interface with Internet should be NAT-ted, the WAN internface with IPTV should be added to the bridge (tagged if it is on a VLAN or untagged to seperate it from the rest of the network).
Please read this great tutorial:
http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1