If you're planning on multiple staff using them then worth bearing in mind that each would need to do the courses Rilot mentioned at about £1,000 a pop and 3/4 days away. Your Operations Manual will need resubmitting with each new addition/removal of operators too (at cost) which can take a while to get approved.
You also need to name someone who's solely responsible for the airworthiness of the craft and equipment (and prove they can do this of course) which might get complex with lots of operators/national sites etc.
Just so you're aware!