Potash is the third most necessary plant nutrient, while blood, fish and bone provides mostly nitrogen.
The time to apply is just before or when grass or plants are in vigorous growth, otherwise you are wasting the feed which will wash out during the winter rains.
The nitrogenous fertilisers are best for grass if you want lush, green growth that crowds out the weeds.
Potash is possibly better for borders.
Don't forget that for lots of flowering plants in your borders, if you give them too much feed you will get large, leafy plants at the expense of the flowers. Keep feed to a minimum. You could try foliar feeding them to keep them healthy with a spray of seaweed solution or a proprietary feed like Miracle-Gro or Phostrogen.
I'd keep the blood, fish and bone for the veg. garden unless you have hungry trees or shrubs.

you could not get a more compleat and correct answer that Bertie has given you , so I will shut up' and let you digest what he has told you.

I'll add a bit here - I never use fish, blood and bone as a general top dressing in the top of the soil, always at the bottom of planting holes, or when doing a thorough dig. Cats and dogs like it too much, keep trying to eat it if its on the surface.
Sulphate of potash encourages flowering so, for instance, a top dressing of this sprinkled in late February on the soil round raspberries will encourage more flowers and thus, fruit.
For general garden use, I recommend Growmore applied in April, when you turn the borders over, and for the grass, a proprietary lawn feed, usually combined with a weed and moss treatment too, but you can just get granular lawn foods, or a liquid one to be applied by watering can.
Growmore can be reapplied 6 or 8 weeks later in the same fashion to the borders, if you think it necessary.
Pots and containers need different treatment.