If you head to your local halfords they have booklets that show all the bulbs needed for all mainstream cars. I would put money on it that the one you're after is in there.
If it's stop and tail, then it's likely to be a 380, if it's a brake light bulb only, it's a 382.
The difference is that they both look like miature household bulbs, but the:
380 - has two filaments, one higher than the other, and has two contacted on the bottom
382 - loks the same, but only has one filament and one contact.
However, there are about 6 or 7 different bulbs that are used as brake light bulbs, but my old Mondeo used to use the 380