Most listings are in the $20's per square foot per year. The Heathrow region is seeing a a boost 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 posted online, which means spaces most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. 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 buildings in this region are close to 3 stories. Most buildings in this area were built in 1997 and are Class A.