Gents,
Many thanks for the pointers, I'll return the necessary values without using String and continue on.
It's difficult to know everything you need to when you've only done the Kit Exercises and then started off on a project that will motivate enough to continue. You learn from your mistakes, us newbies simply can't accrue all the necessary knowledge up-front, and trawling through the forum and internet doesn't always answer a question that you're not really sure you've identified yet.
Rather than hang my hat up (I'm feeling a bit demotivated now), I'll soldier on and see if I can get the HW to do what it's intended to do, this ultimately being the goal. I'll learn how to tidy and streamline the code as I go (with a LOT of help) but will try and have a better picture of the issue before asking a question.
Once again, many thanks for the help.