I think you should speak to a solicitor.
You have been caught drunk driving at 3 times the legal limit whilst banned for 18 months a year ago, the court will certainly ask for a pre sentence report and will warn you that custody could be an option.
You are likely to face a 3-4 year ban, and a community penalty if you are lucky enough to avoid prison.
You should make sure that your solicitor asks for you to be offered the Drink Drive Rehabilitation Course as that will take up to 25% off your ban if you complete it. The court may order you to attend a Drink Impaired Driver Course (DIDS) as part of the community penalty. That is compulsory and is 30 hours over 15 weeks. This does not, however, get you a reduction in your ban which is why the DDRS course should be requested as well.
You will also face a big obstacle getting your licence back at the end of the ban. You will be viewed as alcohol dependent and will have to satisfy DVLA that you have not consumed alcohol for at least 12 months.