Or, you can set up a tunnel to forward HTTP traffic through a host at your work. This works if you have a small number of hosts on the workplace intranet to which you wish to connect.
Using your example host 'work':
ssh -L 12380:someWorkHost:80 -L 12480:someOtherWorkHost:80 work
This will set up tunnels through the host 'work', to the other hosts on your work intranet: 'someWorkHost' and 'someOtherWorkHost'.
In your browser, you would then connect to the HTTP server 'someWorkHost' using the URL 'http://localhost:12380/...'. The choice of local ports to use (12380 & 12480 in my example) is arbitrary, except they should be greater than the reserved port numbers (1500, IIRC). Use a 5 digit number less than 65535 and you'll be okay. If there is some easy-to-remember number, use that.
This requires, of course, a compatible system named 'work'. If the one you are presently logging into to run Firefox is almost any Linux host, it should work fine.
This method can be used to tunnel any traffic, not just HTTP. The remote port (80, in the case of HTTP) would need to be set appropriately.
This method will tunnel HTTP traffic, as opposed to all X traffic as you were doing previously, and should result in an accordant increase in speed.