Most listings are in the $10's per square foot per year. The Brent region is seeing a a boost in rates. In the last 3 months, the median rate went up $0 per sqft per year. That's a 1% increase in rent.
In the last 90 days, 10 listings have been made available, which means new availabilities most likley are leasing quickly. You'll want to be prepared to make an offer immediately. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 640 sqft. Most properties in this area are around 1 floors. Most buildings in this market were built in 1975 and are Class Class C.