Now this is very interesting. I can see why you think it is a megalite goldy, the supports particularly indicate that sort of thing, and it definately wouldnt suprise me with Merlin seeming to have a better relationship with Intamin, where as Tussauds seemed to stick with their faithful B&Ms. And on one of the photos from screamscape the track shown on the plan looks very much like how the track was marked on the stealth plans, so i do believe it is most likely intamin. I dont see why it would be a premier when one of the plans clearly labels it has a lift, rather than a launch. However, the switchback section is the tricky bit. I cannot imagine a mega lite having backward sections, surely it would be very pointless, and changing direction would require some sort of launch or another lift to gain momentum again?! To me this changing direction doesnt seem very plausible. In which case the idea that these switchbacks are indeed immelmans or dive loops is probably very likely.
http://publicaccess.staffsmoorlands.gov ... 2030-FUL(D)%20(14449).JPG
Notice this plan. Look at the curved track entering the station building, just above where it says "New Station Building". Like Gouldy pointed out, you can see that the supports show the track is high up, particularly with the lateral bracing. Then it exits travelling in the opposite direction, and the jagged lines on either side of the track following the contours of the helix round, clearly show either an underground tunnel or trench much lower down, which the helix dives through. The ride is obviously travelling at speed here. The most obvious and likely situation is a dive loop. I just dont see how it would be a switch back of sorts. That would mean the ride would have to change levels dramatically, as well as change direction. Meaning the train would have to slow down. How then would it enter the helix in the trench at speed? Unless there was a very short launch but i doubt that there is room for this much to happen in doors. So in my opinion these sections will probably be dive loops, which leads me to believe this isnt a mega-lite.
However, the most similar track style i can seem to fit with all the evidence is a multi element type coaster like Maverick, just much smaller, obviously, and without the really steep drop (after all, alton towers would never have a drop steeper than oblivion, otherwise it would totally undermine the idea of the ride).
If you notice as well, this ride covers a much larger area that it first seems. Compare it to the curves on rita. The journey out into the woods actually looks quite big, much bigger than i first thought when looking at the plans. And judging by the side views on screamscape, the hills seem to show the ride is travelling at quite a speed, because all the peaks look quite shallow, like they are taken fast for their height. But how would this ride pick up that much speed with a lift hill of only 60 - 70 foot? It surely couldnt. Unless it was similar to Maverick in certain respects, for example, having the LIM faster lift. Because remember, this lift could be a little bit faster than Mavericks, because the drop would be nowhere near as steep, and this would provide the necessary speed the layout seems to suggest with the shallow long peaked hills.
Anyway this might just be me hoping. But right now, from my first few looks at the plans, it is the first solution to the problems that springs to mind. Maybe anyway.