Yes you have to do them again sadly, but you don't have to take an approved ground school as you've already done this for the ATPL's.
Once you've done the 7 they are good for another 3 years without the IR but if you enroll in an approved IR course before the end of the 3 years then the exams will hold until completion of the course even if that takes longer. You should notify the CAA if you are doing this though.
If you complete the IR then your full ATPL exams are good for 5 years from your last IR skill test or renewal. So if you have an IR for a few years without doing the ATPL skill test and then let it lapse, you still have 5 years to renew your IR without doing the exams again.