This tree is actually noted for being fairly drought resistant - the advice you've been given about watering regularly is because it's a new tree - all new trees, until they're established after a couple of years, need extra care to provide enough water till they do establish themselves, by which time they cope for reasonable periods without water because they find it for themselves. However, as you've got yours in a pot, you will always have to take responsibility for watering it -- generally, the foliage excludes most rainfall anyway. It is also suitable for growing in a large container, though will need cutting back to keep it smaller over time. I believe Tugbrethil also advised you that this particular tree is often late to come into leaf, and is always later than most other trees.

having looked at your original question on this tree again, I see you did not say it was in a pot - if you put it straight into a pot last autumn, and left it out all winter, is it possible the pot got frozen for longer than a week? If it did, there's a chance your tree has died during those arctic conditions. Also, the advice you were given regarding watering was on the assumption it was in the ground, where it's much more difficult to make sure the plant gets enough water.

The ones we grow in pots in the nursery require watering 2-3 times a day during the summer. It may not be so bad in the UK, but if you go on holiday, the treee will probably need a sitter.