PPTP connection routing of VPN users http requests

I have managed to set up my PPTP connection and am able to dial in and see all of the machines on my local network.

My question now is this. Is it possible for employees in the UK to dial in to the local server (US) and use the local router to process HTTP requests?

I would like for it to function like a proxy, I presume. The employee already have and ip on the local network, how can I route the HTTP requests through the local router instead of the ISP in the UK?

In mangle set routing marks for all traffic destined to the usual HTTP ports (80,443,8080,8888 etc.), and install a route for that mark via the PPTP tunnel. Ensure the remote router knows how to NAT that traffic out to the Internet.