Just wanted to say that I have gone back through the whole pattern again checking measurements and have drafted the offending border onto paper, cut everything out, marked all the seam allowances and stitched it together, and it is again too short.I still had thoughts that it was my error, but there is no 'slippage' using paper and the seams are dead on !!
The good news is that the rest of the pattern seems sound and I will give it another try in a few days after I have adjusted the offending pieces - right now though I am off to bed with a thumping headache !!!