VPN Dial on demand & BranchCache

We have 3 sites of single PC's (running Win 7 Pro/Enterprise) and are looking at a way of dialling into the office on demand.

The 'easiest' way would just be to connect into the system by manually clicking onto the VPN dialup connection, however if there was some way to automate this it'd be great.

Something similar to how RRAS background dials into another site when it requires access to a (mapped) different subnet for example.

We want the connection to fall off as requred (disconnect after X minutes of activity) to ensure unneeded bandwith isn't wasted. I have already disabled the gateway option in the VPN dialup to inhibit all traffic passing through the main office site (internet traffic for example).

Also as part of this we are looking at BranchCache for the offsite PC's to centralise data. Most of it is documents but so far for Windows 7 the information available is vague.

If anyone could suggest ideas or assistance on how to allow automatic dial-on-demand VPN access as well as any info on BranchCache that'd be great.