ssh tunnels

All,
This is a tricky one but any help would be appreciated.

I have a computer (linux) at home running Debian unstable to manage my ADSL
connection; I use iptables to manage the firewall and also have a small
local LAN connected.
Where I'm working atm , they have fairly harsh firewall rules such that they
block all outgoing ports except 554 (streaming video something or other).
I have a dialup account specifically for work access but I wanted to access
work via my ADLS connection so I came up with this:

(from home)
reconfigure sshd to listen on port 554
setup dialup to work on ppp1 (ppp0 is ADSL connection)
add a route for works net work to use ppp1
$add route -net 132.146.0.0 ..... dev ppp1
connect into works machine
$ssh <user1>@<132.146...>

(on works machine)
$nohup ssh -p 554 -T -R 3127:127.0.0.1:22 <user2>@<home ADSL ip>)
$exit


(on home machine)

$ssh -p 3127 <user1><@127.0.0.1

works a treat...I'm now connected to work via my ADSL link...
I can now disconnect the ppp0 dialup link...or so I thought, as this causes
the link to drop with the message 'connection to 127.0.0.1 closed by remote
host'

I have even tried to get someone from work to setup the tunnel and if the
dialup is connected it will kill anything that is using 127.0.0.1....if
however the person from work established the tunnel without my ppp0 dialup
present this doesnt happen (obviously)

Any ideas as to why 127.0.0.1 should be affected by ppp0 disconnects are
greatly welcomed.
-Chris