If you are a full-time PhD student then are you able to take 10 weeks away from uni?
Most research councils stipulate that if you are a full-time, fully funded student then you are allowed to do paid work for 6 hours a week. (this will all be in your contract or on the website for your research council) Realistically they probably won't find out and if it's related to your PhD topic then they would probably turn a blind eye anyway.
However... when working at a company doing research you are often required to sign a declaration about intellectual property - ie anything you discover/find out is owned by the company and not by you. This means they may not allow you to use this for your PhD. Of course, I don't know what discipline your PhD is in, I am in science and it may be different for other subjects.