A simple licence agreement for a fixed term of up to a year, rather than a traditional long-term lease that can so easily become a millstone if circumstances change.
All the chores and costs associated with maintaining and running a building are taken care of. So, too, are reception and admin staff, furniture and utilities. If you need occasional admin assistance, or a meeting room, they're on hand - you pay for only what you use. Back-office support includes quality copying facilities and mailshot distribution and there is AV and other specialist equipment available to hire.
Heating, electricity, commercial rates, water rates, maintenance and cleaning are all included, leaving you to concentrate on your own business.