Franco Sotgiu and Simon Pogson, co-owners of the three-strong burger-led restaurant group, plan to merge the adjoining sites to create the company's largest branch so far.
The refurbishment, which will start next month, will include the creation of a new bar area, private dining rooms, new kitchens and a bespoke meat ageing room.
Sotgiu and Pogson said the acquisition was part of major expansion plans for the business with sites in Leeds and Liverpool also being considered.
"We've been keen to expand North and Preston has always been one of our target cities; when Paul asked us if we'd be interested in the site we did the deal in a matter of days. We feel Preston has massive potential and are keen to bring our style of exciting food there as soon as possible," they said.
Heathcote put the restaurants on the market last month after 20 years of trade to allow him to focus on his contract catering business Heathcote & Co.
Solita's acquisition of Heathcote's restaurants follows the recent purchase of Aumbry and Bombay sites in Prestwich, which Solita plans to open as a wood fired pizza and craft beer concept this autumn.
The company currently operates sites in Manchester's Northern Quarter, Didsbury and Prestwich and is about to launch a steakhouse in the city's Barton Arcade.