research into production 3D printers has found that the stratasys fortus 250-350 and 380 do not have heater beds. is this correct and is there any issues with product distortion.

They have heated build chambers.

I can assure you that the print beds are held at a constant 78C for the 250.

Fortus 380MC build chamber sets at 95C for Nylon 12. No issues.