If the doors are only 3feet wide * 2 and 1 foot in between you are only
talking about a 7 foot opening. As long as there are no apparent flaws
with the existing wall I would buy a catnic lintel (subject to what is
above) to suit and get a recommended builder to put in or advise.
Building regs are probably required but they will accept an off the
shelf lintel. Again a good builder will have had the experience.