Welcome.
St C's Way is a good route. One day to Jedburgh, another to Kirk Y, third day to Wooler and fourth to the Gt North Road at Fenwick. There's some beautiful remote country and the first day is the hardest, crossing the Eildon Hills and later entering a maze of loops around Harestones. Do that and you'll be fine for the rest.
After Fenwick you've got the crossing to Lindisfarne. Go on a falling tide, starting once traffic can begin to move over the road causeway then, after the bridge over the channel, pick up the Pilgrim crossing, marked by poles in the sand and for a nasty short stretch, mud (it's at the end of a fragment of salt marsh that you cross). We did the crossing barefoot in October, and for an hour afterwards I couldn't feel my toes. However, the mud contains the wellington boots sucked off previous walkers, so they're not a good idea either. And it'd overtop walking boots.