Best way to get th sprowston norwich?

hi im goin to sprowston norwich in a few weeks im just wonder the best way to go. i live in chorley lancashire thats nr preston.when ive looked on google maps and aa maps it says the a17. people ive spoke to say get on the m6. on google maps its say s that is 1 and half hours longer. im goin on a saturday morning setin off at 6