Barry,
Just a suggestion for the next KS.
Instead of setting a goal for a unit of X figures, why not set goals for individual figures, for example:
Goal 1 - Cannoneer No. 1
Goal 2 - Cannoneer No. 2
Goal 3 - Mammoth Rider No. 1
Goal 4 - Cannoneer No. 3
Goal 5 - Cannoneer No. 4
Goal 6 - Character No. 1
Goal 7 - Mammoth Rider No. 2
Goal 8 - Character No. 2
Goal 9 - Mammoth Rider No. 3
Goal 10 - Character No. 3
Goal 11 - Mounted Character No. 1
etc.
Presumably each goal would be quite low (<£100/figure), so based on the current crop of backers, you'd quickly meet the early goals. Failure to hit higher goals would simply mean units would have fewer numbers of individual figures but, importantly, different unit types could be created to make up an army and you could pick Mammoth Riders for either units or characters.
Based on the artwork, if the Mammoth Riders are pretty much identical below the waist, it could be an easy set of goals to get them released?
Looking at your current pricing, each figure is around a £1 or so, so people would probably be happy to put £30-40 in. With 40 backers, the early goals would be a snip.
I can't help but think that this approach might result in higher backing. Worth a try? We could be certain of then getting both Cannoneer and Mammoth Rider units and at least mounted characters.
Assuming my guess of £1/figure and £100/goal is right, at the current level of backing, we'd have 20 goals unlocked (less Kickstarters cut presumably). Even if you only got half that, almost all of the figures I've mentioned above would be unlocked. Backers then just let you know how many of which figures they want for the amount they've backed. If that makes sense?
Edit: In fact, now that the Armoured guys are unlocked, if you did this much lower level of unlocking for individual figures now, I'd almost certainly chuck in enough extra cash for up to 4 units of Cannoneers if two or more individual figures got unlocked, probably more if Mammoth Riders were in the picture.