Heathers like ericaceous soil so perhaps need to be in a corner away from the other plants, unless your other planting also likes acid soil.
My heucheras got vine weevil, sadly, but check exactly what type of soil they like before you invest in them.
as everyone else says, compost and any type of soil improver and check to see if your would-be plants like rich soil, if so then add manure, which you can buy in bags.
I bought compost which was suitable for shrubs to top-dress roses, clematis etc and it is supposed to enrich the soil for five+ months.
Try to remove all the pine needles.
Have you checked the pH of your soil?