What do you mean the
CDT test doesn't work for you? Have you had a private test? Did you stop drinking before this test if you had it? Has your GP tested you and told you that you have a metabolic issue regarding CDT.
It is very unusual to fail a CDT test other than through alcohol consumption.
I don't know why the DVLA are/were reluctant to give you details of another practice. They normally select the one closest to you using post codes, but often these are not the easiest to get to and I would imagine if Tillicoultry was your first option and then they gave you Coatbridge, it would not be that easy to get from the Stirling area to where I know this practice is in Coatbridge.