Yeah Craig, right as usual 8)
Contrails are water steam that stucks on particles from the jet exhaust. Depending on airpressure and winds those can be visible for quite some time, and they can be very beautiful aswell (maybe somehting you can shoot Craig, I'd love to have those as a desktop background!)
Vapour trails are created when an aircraft travels thru air which has a relative high humidity. Air flowing over the wings moves faster and with less pressure than the surrounding air, and the lower pressure causes the water particles to condensate much faster, thus creating a visible trail.