Trying to publish Exchange 2010 OWA on TMG

I am attempting to publish Exchange 2010 client access externally using TMG 2010 and im hitting a brick wall

The environment

1 x TMG
2008 R2 VM
1x DMZ Nic with IP from DMZ subnet, Default Gateway set inc DNS
1x LAN Nic with IP from LAN subnet, Default Gateway not set, no DNS
Routing table updated to allow routing to LAN subnet and DNS resolves internal server names and mail.domain.com

2 x Exchange 2010 multi-role servers (SP3 ru10)
2008 R2 VM's

TMG Config
Installed as an Edge Firewall

I pretty much followed this article to the tee - http://blogs.technet.com/b/exchange/archive/2010/07/16/publishing-exchange-server-2010-with-forefront-uag-and-tmg.aspx cross referencing other articles on the web

Cert installed and valid

Web listener created requiring SSL, listening on the External network, HTML Form Auth & SSO to domain.local

Web Farm created and added by host name - Test run and seems OK
 
Outlook Web App rule created (i will create Activesync and Outlook Anywhere later) - published to the farm, requires SSL, set to mail.domain.com, Authenticated users only

When this is tested from an external source i either get page cannot be displayed or err_tunnel_connection_failed dependant on browser

When i look at the TMG logs i see the following

two initiated HTTPS connections from External to local host followed by two Closed connections with the error - A connection was abortively closed after one of the peers sent an RST packet

Everything looks OK from within TMG, and all the tests/check paths come back successfull - I can browse to OWA directly from the TMG

Any Idea's please