I've never seen seed cones on a cedar less than about 8-10m tall (and often not until a lot larger than that). Pollen cones do appear on smaller/younger trees, from about 4-5m tall. Seems to apply to both seedling-grown and grafted trees.

Whether it is age-related, or size-related, I don't know; if size-related, you could be in for a very long wait with a dwarf cultivar!

Resin

Smaller specimens make cones here. An example of a steel or marine blue Himalayan cedar cultivar sold as a weeping Cedar-of-Lebanon recently had seed cones in a neighborhood near me. The tree is maybe 8' tall, if that.

At least initially, 'Silver Mist' will probably need to be planted in some shade. I'd focus on that initially. If it cones some day, consider that a bonus.

"At least initially, 'Silver Mist' will probably need to be planted in some shade"

Any reason why? I presume that as a grafted cultivar, the foliage is already physiologically adult, and adapted as much to full sun now, as it ever will with time?

Resin

One of the bleached foliage forms from Vancouver Island. These can be delicate. Look in your Welch & Haddow: (Not hardy in UK.(

Here is a link that might be useful: 'deodara silver mist' - Google image search