I have a scissor jack that came off a Citroen Psarra that I used to own (and was scrapped---hence the jack). I have also at one time carried a small hydraulic jack in the front, along with a square piece of wood on which the jack (of either type) can stand on; very useful if you have to do the wheel change on a poor surface. I would also suggest that you carry a "wheel removal bolt" with you. These have been discussed previously and are basically a loooong bolt, of the correct thread, but with the head of the bolt removed (try B+Q for long coach-bolt). The trick is to remove 1 wheel-bolt and then insert the tool into the wheel-bolt hole---remove all the other bolts and remove wheel LEAVING TOOL IN PLACE. When you come to refit the wheel, especially a rear wheel, you have a guide onto which you can slide the wheel into place. For people who have late 126 hubs (98pcd) the early M/Benz tool fits! (for 190s 123s etc).