Welcome to the forum, you will find lots of support here so do ask any questions you have.
Waiting for appointments seems to be more and more typical at the moment as there are many more people being diagnosed as both Type 1 and Type 2 as a result of Covid not that that should be an excuse for such slow response but many surgeries do not have a diabetic nurse but it does mean people have to take a proactive part in managing their condition and educate themselves.
As everybody is different and therefore have to find an approach with they enjoy and is sustainable, some find a kick start with a shakes based dietary approach, some low calorie and some low carbohydrate but as it is carbohydrates that convert to glucose reducing those in your dietary regime is important regardless of whether you are on medication or not.
While waiting until you get your appointment there is still plenty you can be doing to improve your blood glucose.
You may of may not be given a blood glucose monitor, most GPs will not unless you are on medication that could cause low blood glucose so many self fund, inexpensive monitors can be bought on line the GlucoNavii or TEE2 have the cheapest test strips.
But getting a monitor allows you to take control over your diabetes.
I am a fan of a low carb regime and found this link has all the principals which encompass that approach. There are some do's and don'ts and some meal ideas.
https://lowcarbfreshwell.co.uk/
People have the idea they have to cut all carbs but that is NOT the truth but the standard NHS advice suggests rather more carbs than many can tolerate.so it is a losing battle to reduce their blood glucose and more and more meds get prescribed. That is not to say some people will need help from medication.
A maximum of 130g TOTAL carbs per day is a suggested starting point but some people will need to go even lower than that.
Unless people need to have low fat for other medical reasons then normal healthy fats and protein, meat, fish, eggs, should be forming the main part of your meals with vegetables and salads and fruits like berries.
How much work you need to do depends on your HbA1C and if you are on any diabetic medications.
You still need to be proactive and press for your appointments.
A good place to look is the Learning Zone (orange tab at the top) as there are also information and links.