Most corporate uses of proxy servers include the caching of web pages to save on external bandwidth, as well as to impose corporate policy on employess (no browsing the Barely Legal website, etc). The other is providing an SSL gateway to access systems behind the corporate firewall, mostly for remote administration (ala telnet or X11). These are usually UNIX/Linux and not Wintel based.
So, tell me in detail (#of systems w/OS, services, etc.) what you want to do remotely via your home system(s) as you set in the Pub drinking your cider. iwo:
To access your home systems from the Internet, you must have either DSL or broadband cable service.
Costs: initial $150; recurring $45/mn
Now, you can either:
1) Follow a classical, non OS specific approach; you will need to establish:
domain (e.g. oceanbytes.com)
dynamic DNS (e.g. seawasp.oceanbytes.com via e.g dyndns.com)
for XP, install Apache web server, IP Switch WS_FTP server, and configure using XP administrative tools both terminal and remote access.
configure as an Internet gateway for the other local systems, as this system must be directly visible to your ISP (no NATing router/hub). This system must of course have at least two ethernet ports (Gbit preferred).
Costs: initial $500; recurring $100/yr.
2) Use GoToMyPC from Citrix. Most corporations use Citrix for off site access to their intranet and Wintel based applications. Rock solid but Wintel specific. Copy and paste is a nice alternative to ftp if your not a Unix type.
As an added bonus, it can be installed on your PC at work for similar access from home.
I don't actually require access (or files) to the home computer - just to use its internet connection. I thought there may be a way of setting the computers up to do this?
If your ISP allows only one MAC, you can use a rounter/hub with NATing to access the Internet from multiple home computers. Proxies provide caching and access restrictions which is not required.
If I understand your requirements correctly... you want to offer controlled access to the Internet, much like hotels do today.
Take a look at ZoneRider http://www.zonerider.net. I used this SW to set up a local "hotspot" incorporating a standard Linksys wireless router/hub with high gain antennas attached to a gateway server having broadband cable access.
You can grant free access or charge for it (like your girl friend does).