I had my fan belt snap on the M5. With the ignition warning light on and the temperature rising quickly I went straight to the hard shoulder. I cut off a length of windscreen washer tubing and made a temporary belt from it, and when I started the engine it slipped a bit but it did turn the alternator and water pump provided I kept the revs low - too fast and it slipped too much to be usable. With my temporary repair I could drive at 40mph in top, and I limped along to the next service station where the petrol bit sold me a replacement fan belt. I fitted it and completed my journey.