Indexing 6 sprocket rear derailleur, having trouble reaching largest sprocket
Returned to this this morning, and have found that the high limit screw could be let out a bit more, and now that is done the chain reaches the large sprocket just fine! Apologies for being dense!

I am now finding that I can index it fine for going up from the low sprocket, or coming down from the large sprocket, but not both, but I'll work on that....