This article has some more interesting details about the actual staffing and what their manufacturing investments are:
Skylon spaceplane's inventor sees busy spaceports coming soon - Sen.com
We’ve grown steadily. If we go back to 2009 we were about 15 people, and now we’re getting ready for quite a major ramp-up of staffing capability. We’re up at about 65 staff this week, and over the next year to 18 months, we’ll probably expand by about another 110 people.
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....But now we’ve got to the point where we want to build heat exchangers like that on a regular basis, so we’re installing our own massive vacuum furnace and so on. Our own factory will take another year to 18 months to get operational, but then we’ll then be able to build heat exchangers for real spaceplanes! We’re putting in the facilities that we’ll need for future manufacturing in the company over the next 20 to 30 years.