Simple answer to your question about diabetes and blood pressure is that both will be treated separately, however as the GP will always (should) treat a patient as a whole person then they will also have to be considered in tandem when prescribing. The GP has to look and see if any particular medicine has a detrimental effect on either the diabetes or blood pressure. They would then prescribe accordingly.
If, for instance, you maybe needed to lose weight to improve your diabetes and your control was also good, your insulin resistance improved then that could also help to improve your blood pressure over time. A knock on effect. Taking measures to control your diabetes is not always a quick fix.
However, many blood pressure medications can swiftly lower your high BP down to the target of below 130/80 which is recommended. Taking away one problem which would then allow you to concentrate on the diabetes control.
Both conditions are important to get control of, as to which has the highest priority only your GP will know. May be an idea to discuss your concerns with him/her as well as on here. You can also discuss if you are diabetic or not.