My cover with petplan from the 4 weeks free was considered as the same policy. I was not given a new policy number, it just carried on. There was no break between policies and so my kittens were covered for their TF treatment even though the testing started months earlier when on the 4 week free insurance. I would check again and ask them what is the point of the free insurance if you are not protected once continuing the policy. There is no benefit to the customer from taking theirs out over a competitor...!
It cost £65 recently to have the full PCR screen at my vets who sent the sample to Idexx labs. I popped the info for this in you other thread i believe.
I don't think you will get the tablet for your kittens as i believe the dose would be far too great for them.
I also wouldn't test Chilli and Rio separately. I would pool samples together and send off that. Chances are they are both positive and if one is negative you must either treat anyhow or isolate for the two week treatment plus 2 weeks to make sure that no cross contamination happens where Rio passes it onto Chilli before it is killed properly and then Chilli can pass it back to Rio again.... If you are not prepared to separate the cats (i wouldn't myself) then it is essential to treat both.