I have set these up in the past but this one isnt working. Both are 2820n and configured as follows:

Profilename lan2lan
Enabled
Dial Out
Always On
Keep alive by 10.1.12.10 (remote server)
PPTP
Username - lan2lan
Password ***
PAP/CHAP
VJ Compression ON
Server IP - xxx.dyndns.org (resolves fine)
MyWan 0.0.0.0
Remote GW 0.0.0.0
Remoet Network IP 10.1.12.0
Remote Network Mask 255.255.255.0
RIP Direction - Disabled
From first subnet to remote network you have to Route

Profilename lan2lan
Enabled
Dial In
PPTP
Username - lan2lan
Password ***
VJ Compression ON
MyWan 0.0.0.0
Remote GW 0.0.0.0
Remoet Network IP 10.1.11.0
Remote Network Mask 255.255.255.0
RIP Direction - Disabled
From first subnet to remote network you have to Route

In the VPN Connection Management, I get a connection listed, but cant ping the remote network from either direction.

Any ideas?

The alternative is to get the VPN Lan 2 Lan going the other way but 10.1.11.10 server is running VPN so it would have to be a Draytek to Windows Server VPN. Is there any how to on this one?

maybe "but 10.1.11.10 server is running VPN" this has something to do with your problem ?
If a server inside the 10.1.11.0 network is running PPTP-VPN you might have redirected ports/services to this machine, which will most likely make it impossible for the 2820 to serve as a VPN dial-up server.

Suggestion:
Disable the PPtP service of the vigor in the 10.1.11.0 network (it does not work anyway)
setup a Lan2Lan connection using an IPSec tunnel between the two sites.
If the site which dials the connection is on a dynamic IP Address:
(on the site, which dials the connection, enable aggressive mode, and PFS, enter some random credentials for the identification, on the site in 10.1.11.0 network, specify these credentials under "peer ID", under Preshared key enter some random string >20 bytes size)

the 10.1.11.1 router has all vpn options in remote access control disabled since it isnt receiving any connections. I have configured this router to dial out to the 10.1.12.1 router via pptp and it does connect, but I dont seem to be able to get any traffic through?

I never tried this variation, however, I think If you disable any VPN service, the router will most likely be unable use it, regardless, if it is the initiator or the responder.

Why dont use PPtP for the dial-up networking of the Windows server, and use IPSec for the Lan2Lan connections via the draytek ?

I think that using the server and the VPN server and the draytek as the VPN client is working. I will try with the client later and report back.

nope, it isnt working, shows as connected, but no ping replies