First off let me say that I am only a home user with a bit more knowledge.

Next, PPTP is not very secure and quite easily crackable these days. The consensus seems to be that OpenVPN is possibly the best available, easily configurable option for teleworkers. Another option is L2TP over IPSec but I'm not sure what clients are available.

For a bit of fun I moved away from a Draytek router and now use a PC running ClearOS as a gateway as this give far more flexible solution, and can run on low cost/low power boxes such as Intel Atom based boxes. This has a PPTP and OpenVPN server. It also has an IPSec server but you'd have to learn how to configure it manually for this type of solution. I do have an IPSec VPN from my ClearOS box to my mother's Draytek 2900.

I cannot give a definitive answer about which solutions will work with multiple endpoints behind a single router, but I believe OpenVPN will do it as will some other (costly) proprietary solutions.

cookhamjames wrote: If i were to get the ADSL supplier to assign more than one IP address to the building could I set different cleints to use different WAN IPs to get around the problem?

Pass. I would have a guess the Draytek would not recognise any but the primary IP, but it is a bit of a guess.

If you have Draytek boxes at either end why not do a LAN -> LAN VPN rather than Teleworker -> LAN.

That would open up the connection to the whole LAN....