Hi Neil and many thanks for the comprehensive response. I must be rather dense as after following your advice I can still only see the 'spot height' rather than total height gain. However I've now gone over the route section by section so that I now have the information needed - it's also helped to refine and familiarise the route for me - most of which I haven't walked before.
Thanks also for the tip on predicted v actual mileage, I'll take that into account on my adventure