A great example of why so many brands and businesses need to adapt to social media sooner rather than later and get to grips with branding.
In this case, their usernames across social media are inconsistent and I have seen far worse from established brands.
Using tools such as namechk, you can search availability across multiple social media networks, domains and secure your username.
As an example I use @brianmartinuk across my social media networks, apart from Facebook where it had already been utilised. I have also seen people use NW, NE, SW, SE dependent on the part of the country they’re from. Businesses also use HQ where their names are generic or already taken.
If you’re a business, use the same as your domain where possible.