Are there many PPL/SEP holders, flying as LAPL-restricted FI's out there?
I don't think so. Why would a school want to take on an instructor who is limited to LAPL only, when there is no shortage of FIs who have done the CPL theory and can instruct for PPL etc?
Also, I assume most students now will complete their LAPL's first and then upgrade either straight away or once they have built up some experience.
In my experience, the vast majority of new students want the full PPL, with only medically restricted individuals going the NPPL/LAPL route. In the real world the amount of training required to get to test standard will be more or less the same.