The petrol-powered A200 starts from £27,500, while the more powerful A250 is available from £30,240.
SE models feature twin seven-inch displays, including a central touchscreen and voice activation.
As for what the new model means for the regular GT Coupe, a Mercedes-Benz spokesman confirmed that another facelift is coming for the two-door vehicle, though it's unclear how much of the GT 4-door's ground-breaking interior will make its way across.
Sitting above the updated version of the standard auto but below the fiery C63 V8, the C43's 3.0-litre V6 gets a power boost and a host of minor design tweaks that bring it in line with Mercedes' newer E- and S-Class ranges.
Also standard on the SE are comfort suspension, 16in alloy wheels, DAB radio, Artico leather and Bertrix fabric upholstery, Active Lane Keeping Assist, Speed Limit Assist, keyless go starting function and air conditioning.
The Sport trim line adds LED high performance headlights, 17-inch alloy wheels fabric upholstery and automatic climate control. A 0-62 miles per hour time of 10.5 seconds is respectable, as is a top speed of 125mph. Opt for AMG Line and 18-inch alloy wheels, a sporty body kit, microfibre upholstery and a three-spoke steering wheel are fitted. Its top speed is 155mph.
At least one plug-in hybrid version of the GT 4-door is expected to be added to the range with as much as 590kW on tap and a sub-3.0sec 0-100km/h sprint, however AMG representatives were tight-lipped on a high voltage version at the model's launch. The engine also features in the new CLS AMG, and it is still very quick, with 0-62mph arriving in 4.5 seconds.
A range of three variants was announced, including an entry-level six-cylinder GT53 and two V8 versions, called the GT63 and GT63S. The Executive equipment package costs £1,395 and swaps the standard 7-inch central touchscreen media display for a 10.25-inch item, as well as adding active parking assist with Parktronic, heated front seats and a mirror package.
Premium Plus adds memory function for the driver and front passenger seats, multibeam LED head lights with adaptive highbeam assist plus and a panoramic sunroof.
The Premium pack includes the Executive pack options, as well as the dual-10.25-inch display Widescreen Cockpit, an improved surround sound system and Keyless-go - which comes at a £2,395 cost.
The Advanced Navigation package introduces augmented reality into the onboard satellite navigation.