I did a masters in CS for almost the same reasons and it was one of the best decisions I've ever made. Met a tonne of amazing people, learnt a stupid amount in one year (which I say with some authority in learning stupid amounts in short spaces of time) and had a really fantastic time. I found that it forced me to do things I wouldn't perhaps on the face of it have chosen, but turned out to be really interesting and influence my work in other areas (like predicate logic, which I initially hated but learned to love).