The planet bases are made from concrete sewer pipes.  The tops of the bases are made from stainless steel which was shot-blasted. The bases were filled with concrete and the tops set into the concrete after a few fine adjustments.  Then the smaller planets were screwed in place.  Saturn and Jupiter were welded in place on the stainless steel tops.

Construction of the Sun was another matter.... The Sun is made from 2  fibreglass hemispheres manufactured for a septic tank. A hole was cut into one of the hemisphere and then the two halves were fiber glass together.  Next the internal steel work to support the Sun was installed and the sphere sealed before being painted gold. The supporting steel-work was manufactured by Minster Engineering. The foundations were prepared, 10 tons of concrete poured in and finally the finished model was installed.