Having a second business is normally not allowed without permission. If its not related most employers might be ok. Like a PM I knew at BT who had a side gig a

Having a second business is normally not allowed without permission. If its not related most employers might be ok. Like a PM I knew at BT who had a side gig as a violinist - one year his band had a residency during the Edinburgh festival (at the balmoral no less ) - if it had been a job related to huis day job no way would have he been allowed