Again, many thanks for your help sussamb. I had named the custom symbol I'd created Pin, Blue.bmp but I uploaded the symbol you had attached, renamed that Pin, Blue.bmp, replaced mine with it and that works fine now so I don't really know what I had done wrong, but clearly something. Planning in Basecamp also works fine now that I've selected Direct rather than Hiking.
I'm working my through the guides you suggest and I'm sure I'll be back with more questions but for the moment I am, as I said earlier, very grateful to you for taking the time to help.