Mike there is not a problem with that.
I am maybe being a bit over the top because of my experences with some out of the blue conversions. If you don't know them from adam they can pull some truely bizzare stuff out the bag. Even had one manage to get us nearly into a spin by getting his feet confused and booting the wrong pedal in the tommy. As I said you get some right tulips out there which in some ways are harder to deal with than a ppl student. It looks like Genghis has had a couple of said tulips.
To be honest though if they are 200 plus hour PPL's and are ****e your best not even trying to get them up to standard. By that amount of time all the bad habits will be pretty much ingrained 2-3 hours with anyone you like won't solve their problems. By ditching them you are just protecting your investment.