routing out two ppp lines via source eth - iptables

I am trying to create two tables to route traffic based on the
ethernet port in which the originate.

Basically it is setup like this;

25
------->| eth0 | --------->ppp0 ---------> Internet
| 80 |
| |
| 26 |
------->| eth0:1 | --------->ppp1 ---------> Internet

8080

On each eth interface an instance of squid and sendmail are running
through the ports identified above.

I have scripted the connection for each ppp interface and then followed
up with the following;

#/bin/bash!
p0=`/sbin/ifconfig |grep P-t-P | awk '{print $2}'\
|sed -e 's/addr\://g;' |grep 209`
p1=`/sbin/ifconfig |grep P-t-P | awk '{print $2}'\
|sed -e 's/addr\://g;' |grep 129`
#
echo $p0
echo $p1
# Setup IPTABLES
iptables -t mangle -A PREROUTING -i eth0 -j MARK --set-mark 20
iptables -t mangle -A PREROUTING -i eth1 -j MARK --set-mark 21
ip route add default via $p0 dev ppp0 table 22
ip route add default via $p1 dev ppp1 table 23
ip rule add fwmark 20 table 22
ip rule add fwmark 21 table 23

Unfortunately this is not working - for some reason it is taking the default
route instead of using the rules setup above.

Can anyone shed some light on where i have gone wrong?

Thanks in advance for any and all help

Cheers,

Chris