IVA and credit file

We have 18 months left on our IVA and our IVA company have offered us a loan to clear the balance and allow us to close our IVA within 3 months. They said this will take us off the insolvency register within 3 months and we will receive our certificate. We are keen to start rebuilding our credit rating so we can get a mortgage again. Is this a good way to do this? Will the IVA stay on our credit file for 6 years anyway despite paying it off early and receiving the certificate? Will being off the insolvency register allow us to build our credit rating back up earlier? Any advice would be much appreciated, don't know what to do!