Switching your supplier can be quite different than making the swap at a residential address, with the switching period taking around six weeks. During this time, your new supplier will work out the finer details with your existing supplier and let you know a switching date.
There should be no disruption to your electricity and gas supply, even on the day that the change is made. Generally, there won't be any need for your supplier to make any changes to the infrastructure at your premises, as gas and electricity will be supplied through the existing pipes and cables regardless of your supplier.