Replying to Boot Liners, Fitter's Help Please.

Boots. I hate buying ski boots.
I got fitted at the best shop in the UK and got Full Tilts in the end, even though I didn't particularly want them, they were the best fit for my foot by a long way. I used to have some Head Mojos which were far too wide but held my heels nicely.

I've skied the Tilts around 3 weeks and while the fit on my foot is perfect, I find the ankle hold of the Intuition liner isn't good enough. I've been back to the shop and they've tried to mold in extra ankle hold but it hasn't worked. I still get heel raise when I butter/press and it hurts. I didn't in my old boots even though they were a size bigger and the wrong fit on my foot.

I've concluded that the problem is the liner. When I tried putting my old liners in the new boots the hold was massively better, but obviously the liner is too big for the boots. I want to replace the wrap liner with a regular liner with good heel hold, but I don't know anything about buying liners separately. What liners can I buy? I don't really want a full custom liner, an off the shelf liner is probably good enough!