I put a bit of work in these last couple of nights, and behold - Bumblebee has hips! .....sort of.
Behold the wonder that is PEGBOT - with torso twist action, and, erm, pegs.
Seen here posing with his little mate G1 Jazz. Go fellas!

I'll start off by showing you some detail, and explain as i go.
(I hope the photos are adequate to explain the details!!)
Here is a close up of the hip region in bot mode:

The hips are designed to slide out from under the dashboard for bot-mode - you can see the grooves cut into the plastic to help guide it in. The brass rod in the centre is what allows it to slide smoothly, and is essentially the 'backbone' structurally. When finished, the top of the brass tube will be capped so the torso cant be taken completely off - im leaving it for now, because i will want to disassemble and paint the model later.
You can also see where the hip swivels - in ALT mode, the swivelling is locked when it slides in to the car, and in bot mode, a piece which also supports the bonnet swivels around and locks the torso, stopping it from sliding back down over the waist.
Here is a pic of the whole assembly transformed:

Here, in addition to all the other worky bits, you can see the arm assembly that the bonnet attaches to - at the present, it is too long - it will be trimmed to just past the swing arm attachment at the very top of the photo. That arm swivels to sit at the rear in bot mode, and folds up, making the bonnet a rear armour plate, and balancing out the robot's lower half. The legs need to be trimmed to allow the swing arms to lower into the engine area - at the present, they are stuck in full open position...
Here is a pic of the whole assembly, with the interior detail added to show how all the workings will be covered over.

The dashboard will conceal the upper legs, knees and waist workings, and in addition to the sheath which now covers the 'backbone' sliding parts, there is another piece which goes over it which has the gear stick, hand brake and, most importantly, cup holders. The only sacrifice so far is I had to remove the Jumbo drink holder.....but i dont see Spike as being a Jumbo man myself...
Here is a pic of Bumbles a little more appropriately dressed:

As soon as the swing arm is trimmed down, and the legs altered, i will be able to fit the dashboard and build up the front detail some more, particularly the hip and interior detail. The hips need bulking out considerably; now that i have a better idea of where everything fits, this should be easier to do.
The wheels won't be attached to the upper thighs for a while yet - i need to leave them until the legs and hips are all done, because the correct positioning of them is critical. At this stage, having working steering is probably not going to happen, but i havent given up on it yet...
Well, that's about it for this update, feel free to ask any questions you might have, or put forward any advice.
Also, at this stage it's not critical, but if anyone has some advice on how to dye the styrene plasctic, i would appreciate it - i have read posts where folks have mentioned doing it, but i have never heard of it before this forum, and dont know which products work best, etc. Thanks guys!