If DVLA needs more definite info they will transfer your application request to their medical investigations section (in the next street in Swansea), who may send you another form for you and your doctor/consultant to fill in. They may also request your permission to gain access to certain medical HCP records such as hospital admissions toA&E etc, While you are being investigated, you will be granted temporary permission to continue driving until they close your case. It will delay things but should not stop you from driving unless they discover anything that requires immediate action. Public Service drivers and minibus drivers bars are stricter than car/bike applicants. They may require a special eye test which they will arrange and pay for.
I renewed 3 years ago at 70, and it took6 months and their special eye test to sort out my medical records which included strokes, heart attacks, bypass op, laser surgery on both eyes. I got my 3-year photo ID without argument. and last week sent it off again to renew, I did a DIAB1 at 70, but not for this application since I am on orals only and no change in my HbA1c or hypo status. We shall see if I am successful. In this instance, I was also able to pass on to them letters from my optometrist regarding diabetic eye screening, and an annual eye test at the local opticians, so hopefully will not need the special DVLA tests,
The worst case is that if they think you may be hiding anything from them, they may require a mini in-person driving assessment but the cost of that makes it rare and is mainly for anyone having to use an adapted vehicle. Unlikely just for not being able to get an annual review with GP or DN. I haven't had one either, Your signatures on the declaration is usually accepted.