On average, listings lease in the $20's per square foot per year. The Heathrow submarket is seeing a a rise in rates. In the last 3 months, the median rate went up $29 per sqft per year.
In the last 90 days, 3 listings have been made available, which means office spaces most likley are going fast. 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 1,600 sqft. Most properties in this region are around 3 stories. Most buildings in this market were built in 1997 and are Class A.