You will have to fill in your first application and medical form, then see your GP for him to complete a form confirming that you have 3 months of readings, you have not had a severe hypo in 12 months (they look at anything under 4), and you know how to recognise and deal with hypos. Then you will be sent to see a DVLA consultant to go through exactly the same questions and for him to look at your meter. Be prepared to travel to see the consultant, there are only 55 covering the whole country! As long as you answer the questions correctly, supply your readings for the previous 3 months, have not had severe hypos (including night time ones) and are ok with the new eyesight regs you should be ok.
It is difficult for me to comment on hypos because I am hyperglaecemic (but still get tested under the same criteria for some reason).
As I say, to renew your licence you need to start the process 3 months before the renewal due date....that is contact DVLA and they will send you the pack, send back the application form and medical form. By the time your renewal date comes round they should have completed their investigations and your new licence should carry on from your old one without a break....but remember this is DVLA we are talking about