Simple - you just enter your destination and then select the ‘avoid motorways’ option! That’s exactly what we did recently when we went to Newcastle and found ourselves in a pickle on the A1M, it got us round it nicely.
As to memory, yep, I’d look up the route and remember it. I’ve even once or twice circumnavigated problems without any satnav or map simply by ‘following my nose’ and heading towards places that I know to be in roughly the right direction!

