Make an appointment with your GP and tell him/her that you are applying for your licence back and that you need support in the application process, (there's no hiding from the DVLA ) tell him the truth why you've been refused due to your high CDT level and that your last drink was on x and stick to that date, your liver function test will be proof that you have quit the drink to your own GP and the DVLA, yes your doctor can back date your last drink date and you will need to build a good rapport with him/her, on application for your licence the DVLA will send your GP medical questionarres DD2 for alcohol and M2 for current medication, it will be on this form that your last drink date will be required, I supplied 4 LFTs over the course of a year, it's very important that your GP gets to know you well and your medical background to support you going forward and to fill the forms in correctly as there have been lots of cases where people do not know their doctor and a licence has been refused due to that,( forms filled out INCORRECTLY)and that's the last thing you want as it can put weeks/months on a case..the more liver function tests you can supply the better...