Ok, so this can be a confusing one. As far as I am concerned, you are the owner of your IP and every part of the brand belongs to you. I never re-purpose brands to sell to another client, nor will any elements of your brand be added to someone else’s. For a start, your brand is unique and created for you. Plus, it wouldn’t be a very nice thing to do and, in all honesty, it would be a bit boring for me – I thrive on creating new things! Any brand assets I create are 100% bespoke and owned by you. All I ask is that I use your designs within my portfolio.
However, UK copyright law states that for the legal ownership of copyright to pass from one person to another, a written assignment must be signed by the owner of the work, which all involved parties usually sign once the client has paid for the logo. So, if IP is important to you, I recommend getting independent advice from a lawyer.