Training Espalier Pear Trees

Does anyone have a book or website which they can recommend on training these? I know exactly how it's supposed to work. I'm aiming at an espalier with three or even four tiers, i.e. adding one per year. I've trained an apple in the distant past and it went OK.

However, I need to find some advice on what to do when the tree doesn't behave as expected!

Specifically, it's in its second year of training and the vertical has been cut back, i.e. expecting enough buds to break as a result to give two more horizontals to choose from. These should form the second tier.

However, it is now August. No buds have broken on the vertical stem that was cut back. In contrast, the horizontals from last year continue to grow steadily and will soon be longer than I have room for.

So, I basically need some more vigorous vertical growth from it but I have more than enough horizontal growth. See, I told you it was awkward...

The variety is Jargonelle, the rootstock is quince C. The soil is a rich fertile loam, i.e. almost as good as it gets.

All I can think of is watering the tree more heavily to encourage more vegetative growth. It's so far had no effect.