I received an 18 month ban for drink driving but never re applied for my licence back

When did you receive the driving ban? Is your disqualification over yet?

You do not necessarily need to resit your driving test after being convicted of drink driving. If you have to redo the test, the court will tell you so and will attach a condition to your file. The DVLA won't let you apply for your driving licence when you ban ends afterwards unless you complete the driving test again.

If you can't remember whether you have to resit your test, you can always contact the court where you were sentenced or phone the DVLA and ask them.