Don't use the concertina type bypass hose - you have already seen what happens to it! The best one is simply a piece of thickwall heater hose - although someone on here was selling silicone bypass hoses recently.
Well, I've done everything suggested three times over (except the drain cleaner option which I will try at a later date), and still nothing comes from the engine block bolt so I'm giving up for now.
Took the car for a 30 mile spin and everything seems ok, I could even stick my finger in the rad water for a few seconds without burning my skin.
Piece of bent wire in the drain hole - and wiggle it about vigorously! Drain cleaner (probably sodium hydroxide = caustic soda) should do the job - but don't leave it in for more than an hour, with engine running - then flush out several times.
