Here are two useful links which can help you find your gas and electricity supplier if your agency or landlord hasn’t told you. It takes a month or so for the supplier to act on your move-in and evaluate your supply so it better for you as a tenant to contact, this could be useful for address proof.
Gas: https://www.findmysupplier.energy/webapp/index.html
Electricity: http://www.energynetworks.org/info/faqs/who-is-my-network-operator.html
