barclays bank ppi

ds100

PLease help!!!!
i been with barclays over 7 years during that time i been taking from them 5 different loans and i just realise all of then with barclayprotection payment, the firts four loans were paid early so i should apply for a partial refund or for the full refund cos nobody told me the insurance was optional?
Now with my existing loan in the terms and conditions they said if i canx my ppi in fact i will canx the whole agreement so in that case i will have to make a new application for the remaining balance and in that case they can not guarantee the interest rate or the terms or conditions they offert me in my existing loan so ....i should go for it or i just screw up now big time?

Please help thanks!!!!!!!!!!!!