Roger what you have described was exactly what I went through last November. I am so pleased that you are making such a good recovery (far quicker than I did!) I am impressed that you managed to walk to M&S and back, I couldn't walk up one flight of stairs without stopping 3 times for at least 2 weeks afterwards!
Don't overdo it, it's so easy to want to but as you are coming on in leaps and bounds please stay that way. Take care and all the best
xx