FTE have a huge turn over of Instructors. You will be expected to relocate at you own expense and sort your of logistics in terms of accommodation etc. Pay rates are market average with them and Spain is quite cheap.
Taxation is quite high and you will be double taxed if you have assets outside of Spain which is driving a lot of the Brits home.
They struggle to fill the Ground Instructor roles as you really need to know your onions when it comes their expectations.
They also put people on 6 month trials and often terminate them at the end which is why the jobs are advertised so frequently. This can be a problem if you have moved out lock stock and barrel.