Are you using runners with your Tillets, or the aluminium box section channels, or just bolting the seats directly to the floor?
I have tried many different approaches and found the runners to be the worst, becoming very hard to move once bolted down and getting jammed up with grit over time rendering them unusable. I binned them, they're junk.
The aluminium channels were better and I have no problem using them.
However, the best solution I found was exhaust bobbins screwed directly into the Tillett base with a large penny washer and nylock at the underside of the floor. Exhaust bobbins are cheap and plentiful on eBay and come in a wide variety of heights. I experimented with different heights front/rear to get the exact height and amount of tilt I wanted (which for me was 35mm from / 15mm rear bobbins).
One tip is to use a hole step drill/cutter to enlarge the holes in the floor a bit... or more likely just redrill them where you want.
I don't care that the seat isn't adjustable fore/aft, no-one else drives my Caterham and the adjustable runners are unusable junk that don't work anyway as previously stated.