I read somewhere that the potassium in bananas is supposed to decrease BP. Which seems strange given that sodium is supposed to decrease it. Aren't they chemically very similar?

Bananas are good, berries and most leafy green vegetables. Avocados, sweet potatoes, nuts and legumes.

Switched to potassium-enriched salt for cooking so no-one else in the household has to suffer bland food.

Beetroot juice (+ apple & carrot to counter the acidity) is also something you could try. Actually good for your blood flow with potential flow on effect for your BP.

Personally taking Omega-3 and magnesium supplements.