In reply to idiotproof (Buxton MC):
Similar conundrum when we changed cars last year - no tow bars and the roof bars for my old car wouldn't fit either of the new cars.
Cheapest solution for me was new roof bars that would fit both cars. Whispbar worked out much cheaper than Thule, as I needed foot packs for flush rails for one car and no rails on the other - the bars are more expensive, but the foot packs are much, much cheaper and if I change cars again it will only be £25 for a new foot pack (unless it needs wider bars).
Changing the foot from clamps to rails is a bit of a fiddle, but we mainly use one car and so don't do it often.
Everything you need is here:
http://www.roofbox.co.uk/
Edit - if you want fast, then bolting roof bars to the car, then the bike carriers to the bars takes time. I suspect the mount points on those cars won't be the same distances apart, so you'll need to fiddle each time you change cars.
Sounds like a tow-bar mounted solution might be best for you.
Post edited at 12:19