I'm a Chemiweld fan personally. A mates father is a mechanic and put me onto the stuff. Had an XD when I was 19 and the heater core had blown, which requires the dashboard to be removed. Chemiweld fix lasted 2 years until I sold it, who knows how much longer it lasted. Mum had a 77 3 series BMW with a leaky head gasket, mates father kept it going for 18 months with chemiweld before the head had to come off.
The downside is the stuff can wreak unbroken stuff like radiators, heater taps, clag up internals etc. The above are probable extreme cases and I would only recommend it as a solution to get you out of strife. If I had to use it on one of my current cars, I'd be doing a mega cooling system flush afterwards.
On long trips I always have a bottle in the back of the car.