Why not just buy a bright light, and stick a sheet of
Lee 201 over it. Gel is about 4-5UKP a sheet.
In London, many places will sell it.
White Light in Wimbledon will help, and
Stage Electrics has online shopping, even.
I imagine it'll be way more effective than messing with your computer's colour balance. More powerful too.
Even the
"daylight balanced" bulbs you can buy will probably do the job.
The computer is a versatile tool...but it's not
every tool. Sometimes the solution is outside the computer!