Boot help!

Hi guys, bit of a two parter question regarding boots. I have Grisport Hunter Pro boots (I didn't read the reviews before I bought, more fool me!). They're a few years old and have been used on and off and are nice and soft to the touch. However every time I use them, I get big blisters on my heels. Over New Years, I tramped the Leslie-Karamea, coming out the western end of the Wangapeka. After one day, I had a blister that had ripped open. By the end of the tramp with that blister well taped and padded, it had become the size and depth of a ten cent piece (the old ones) and took a month to fully heal. I also lost three toenails and got another half dozen blisters in various places. This weekend, both heels blistered within an hour of easy tramping up the Nina and we abandoned our plan to make it up to the tops. Flats, hills, rivers, it all gives me blisters in the exact same spot. I don't think my heels are oddly shaped (happy to post a pic for criticism) so I'm trying to work out if there is a way to fix my boots so I don't get blisters on my heels and can do decent length trips in comfort. Alternatively, if there is no way to fix these, I am looking at the Lastrite boots but not sure which I want. Do people recommend the Tramper or the Hunter? And how do these fit for people with slight wider toes/bunions?