Seaweed isn't readily available, but there are a lot of farmers around so I have unlimited access to cow manure (of course, I do have to haul it myself...not my favorite job!!!). Everywhere else that I've lived, I had to deal with heavy clay, and many times rocks...that type of soil was a lot easier to amend and I always had a wonderful vegetable garden. It's really been a struggle here to keep things lush and growing. I'll never have strawberries the size of yours here (right now, mine look like peas), but like I said it gets better every year. I'm not a quitter!
Seaweed for soil addition exists as a meal, crumbs, pearls and liquid.Perhaps a garden center near you would have some...and I know that you can order some on the internet. You could have strawbs like mine...it's not all down to gardening techniques. There are some plants that just produce large strawbs. One is the "Gigantella Maxim" available through the Bakker-Hillegom company. There are others. I have no idea what kind my plants are, as I got them years ago. I like your persistant attitude...it's necessary to be successful.
Robin, I did not have any capucijner seeds here at home, but I will look in the shed the next time I go to the lottie (that will be soon). I have not forgotten you.