it needs to grow in a reliably moist lime free soil in sun or light shade it does not like hot dry conditions that we had early in the year that would account for the poor flower this year

No, Jonbridge, I know that Aberdeenshire did not 'suffer' hot, dry conditions :-)))) The expresion is unknown up here.
I have never heard of Tropeolum speciosum not perfoming well, usually too well in Aberdeenshire. Has it done well in previous years, Bst? It seems to be a plant that likes some gardens and hates others, even just down the road.

Perversely, here in balmy Berkshire, mine is flowering better than it has for some time

I'm still waiting for my seeds to germinate (only four months), but what I found out before getting my seeds was that they like moist, slightly acidic soil. Several sources also suggested that the roots prefer to be in shade.