Edwards at York Road on the town’s largest industrial estate told Mid Sussex Council it wanted to move its headquarters from Crawley and its testing and prototype base from Shoreham.
Councillors read a report saying the changes would mean more than 300 jobs being created.
The firm has now been given approval for a comprehensive refurbishment of its existing buildings and building a two-storey extension, with new car parking.
The present premises at Burgess Hill will continue to be used for research and development, with other work also being done at the site.
The approved scheme includes changes to the existing outside car parking, including the creation of a car parking deck and associated landscaping.
The scheme was approved in July, but was reported back to councillors for a meeting last Thursday to confirm a revised contribution of £146,000 from the firm.
The money would be spent on local transport systems.