I have put together some examples of an ATM, and Dialer interface with virtual dialer interface (as preffered by Cisco)

My device is a 2621xm + ADSL WIC. I shall post a full excerpt from the config:

alex@STUDIO17:~$ telnet 192.168.1.254

Trying 192.168.1.254…

Connected to 192.168.1.254.
Escape character is ‘^]’.
User Access Verification
Username: alex
Password:
C2621XM>en
Password:
C2621XM#sh run
interface Loopback
no ip address
!
interface ATM0/0
no ip address
no atm ilmi-keepalive
dsl operating-mode auto
pvc 0 0/38
encapsulation aal5mux ppp dialer
dialer pool-member 1
!
!
interface FastEthernet0/0
ip address 192.168.0.254 255.255.255.0
ip virtual-reassembly
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 192.168.1.254 255.255.255.0
ip nat inside
ip virtual-reassembly
duplex auto
speed auto
!
interface Virtual-Template1
ip unnumbered Loopback0
ip virtual-reassembly
peer default ip address pool VPN
ppp encrypt mppe 128
ppp authentication ms-chap-v2
interface Dialer1
ip address negotiated
ip mtu 1432
ip nat outside
ip virtual-reassembly
encapsulation ppp
dialer pool 1
dialer-group 1
ppp authentication chap callin
ppp chap hostname YOUR ISP HOST HERE
ppp chap password YOUR HASHED PASSWORD HERE
crypto map SITEMAP
ip local pool VPN 192.168.2.1 192.168.2.254
ip classless
ip route 0.0.0.0 0.0.0.0 Dialer1
!
Detailed explanation and configuration of each:

First we will take the physical interface at ATM0/0:
you will of cource need to configure this with the ‘conf t’ command (to configure terminal) and then enter the interface with the ‘int atm0/0′ command.  then you will be able to type out the lines nescesary:
C2621XM#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
C2621XM(config)#int atm0/0
C2621XM(config-if)#
C2621XM(config-if)#no ip address
C2621XM(config-if)#no atm ilmi-keepalive
C2621XM(config-if)#dsl operating-mode auto
We will now need to enter PVC and enter your VPI and VCI (I have used 0/38)
Next I will put in my encapsulation method under this and then follow that up by giving and entering my dialer pool, before exiting the conf
C2621XM(config-if)#pvc 0 0/38
C2621XM(config-if-atm-vc)encapsulation aal5mux ppp dialer
C2621XM(config-if-atm-vc)#dialer pool-member 1
C2621XM(config-if-atm-vc)#exit
C2621XM(config-if)#exit
C2621XM(config)#
Now that we have finished with ATM0/0, we will have a look at dialer1

C2621XM(config)#int dialer1
C2621XM(config-if)#ip address negotiated
C2621XM(config-if)#ip mtu 1432
C2621XM(config-if)#ip nat outside
C2621XM(config-if)#ip virtual-reassembly
C2621XM(config-if)#encapsulation ppp (ppp over atm)
C2621XM(config-if)#dialer pool 1
C2621XM(config-if)#dialer-group 1
C2621XM(config-if)#ppp authentication chap callin
C2621XM(config-if)#ppp chap hostname (your username here)
C2621XM(config-if)#ppp chap password (your password here)
C2621XM(config-if)#crypto map SITEMAP
C2621XM(config-if)#exit
C2621XM(config)#
I do not use my FastEthernet0/0 port, hence I have configured all traffic from my Router to a switch connected to the FastEthernet0/1 port.
C2621XM(config)#interface FastEthernet0/1
C2621XM(config-if)#ip address 192.168.1.254 255.255.255.0
C2621XM(config-if)#ip nat inside
C2621XM(config-if)#ip virtual-reassembly
C2621XM(config-if)#duplex auto
C2621XM(config-if)#speed auto
C2621XM(config-if)#exit
C2621XM(config)
I have an outside rule as follows for outgoing traffic, and a NAT binding from the dialer for the incoming traffic
C2621XM(config)#ip route 0.0.0.0 0.0.0.0 Dialer1
C2621XM(config)#ip nat inside source route-map NAT interface Dialer1 overload
Finally you can save the runtime and test your connection:
C2621XM(config)#exit
C2621XM#copy run start
Destination filename [startup-config]?
Building configuration…
[OK]
C2621XM#

Please excuse any errors or non-factual comments, I am still learning Cisco.  However I was able to use the steps above to get my internet connection going!
Please comment if you have any suggestions, or questions
EDIT! I have spent the last 3 days trying to figure out why my internet connection speed was OK on my standard Thomson ADSL Router and appeared to be capped at 2.3Mbps on my Cisco ADSL WIC. I tried all sorts, changing the method that the router negotiates with the DSLAMs at the ISP end.
Xilo broadband have been very attentive and patient with me while I logged fault calls before any of the testing

Through some extensive research and reading, it turns out that there are some additional commands that I needed to give for my ATM0/0 interface as follows:

The following is an aditional configuration of SCC clock rates on the ATM interface. Clock rates are set with the clock rate aal5 command and the clock rate aal2command.

interface ATM0/0

clock rate aal5 5300000
clock rate aal2 4000000

dsl operating-mode auto

This has helped massively and has made the connection even better than I could have expected.

Hope this helps anyone having specific problems with similar equipment
on a side note Xilo / UNO broadband for the win! its a refreshing change to have a constant and reliable internet connection and top notch support 24/7
Alex