One day you may want to expand into sales, to using the words let or rent may not help. Think of a name that covers all aspects of property which gives you room to expand.
Do people even care what the name of the letting agent is?
When people need a roof over their heads, they're normally pretty desperate you could probably call it 'Hairy Dave's' & still have a constant stream of customers (in fact 'Hairy Daves' is likely to be an awful lot easier/catchy to remember vs. other letting agents)