That's right - Upavon was to have been the first site, and they were getting ready to do the digging just when the report that killed Blue Streak as a military weapon was being written.
The Wroughton silo model is of an early design - 'lift and fire', as opposed to 'fire in the hole.
If you look at the Titan II, its design is based on the Blue Streak design. Barrie Ricketson, who was effectively responsible for the design, went over to the States in January 1960. You'll notice, for example, that in both cases the tube is octagonal cross section.
Blue Streak was a technical success, but it would have been outdated as a deterrent by the late 60s, which is when it would have been coming into service. The silos would have cost a fortune, and there was nowhere to put them. The other fear was a political one - a premature launch, because we think the UK is being attacked, and so we fire off to prevent the silos being taken out. Aircraft can be recalled.
It's also interesting that what we wanted as a replacement was Skybolt, which would go on the V bombers. A lot of money had already been spent on them. I think there was also a cultural perspective: we were happy with bombers as a result of the wartime experience, whereas I don;t think the politicians and civil servants cared for missiles, which somehow seemed rather alien.