Hi Craig,
Just spotted this thread while having a coffee break and then noticed you had already mentioned my name in your post.
otb has it spot on, getting the right stretches and knowing how to execute them is the key to improving the long term flexibility of a muscle and allow it to work efficiently without the tightness causing other problems. The most common mistake people make is to not truly isolate the muscle they need to stretch and instead end up stretching nerve tissue as they pass across more joints (classic example is trying to stretch your hamstrings but just wind up your sciatic nerve instead!).
It generally just needs people to be given a bit of anatomical/biomechanical knowledge so they can really isolate the stretch to the muscle belly itself, and is often just a case of knowing some ‘cues’ in order to get into the best position to pull one end of the muscle away from the other.
Feel free to drop me a mail if you have questions on a specific stretch, otherwise if you’d like to make sure that your position on the road bike is not putting your hips at a disadvantage (often a contributory factor) then let me know and we can arrange something.
All the best,
Richard