You appear to be right, I always assumed there was a dedicated degree for that and that it had similar names to Computing, but searching for "Computing" on UCAS does seem to suggest it's more common than I thought for true Computer Science degrees. I still think Computer Science sounds much cooler, but it doesn't seem to be the dealbreaker I thought it would be.
This is an assumption that you're making, and it isn't true.
> is there anything to stop me from calling it Computer Science on my CV?
Use the actual name of the course, don't make stuff up. Also, Imperial isn't a sole exception, a few of the Scottish universities use "computing" too.