People are often under the misapprehension that metformin will be a magic bullet in reducing blood glucose without making any dietary changes but it will only help the body use the insulin it produces more effectively but cannot fight against too many carbohydrates so reducing those is an important part of the treatment process.
Many find a low carbohydrate approach successful, that being no more then 130g total carbs per day, it does not mean NO carbs.
Getting a blood glucose home testing monitor will allow you to determine what foods and meals you can tolerate and help you make better food choices. Testing before you eat and after 2 hours aiming at no more than a 2-3mmol/l increase or as your levels come down no more than 8-8.5mmol/l. You can adjust your portion size or cut some high carb foods out depending on your results. Things like potatoes, pasta, rice, bread, breakfast cereals, pastry as well as the obvious cakes, biscuits and sugary drinks which are the big hitters.
People can find a CGM useful but you need to be able to interpret the result and at £40 a pop for 2 weeks is fairly expensive. You can get a free 2 week trial from Abbott for a Libre if you have a compatible phone.
It sounds as if you have had little support from your surgery but now things should be back to more normal so you may need to be proactive about a follow up appointment for those checks.