Keith,
The current wheels have 56 spokes (...each). The previous owner did run 15" wheels at some point in the past, but went back to standard size wheels & tyres when he installed the current wheels. He had the suspension completely overhauled a few years later and I have not been able to spot any suspicious looseness or faulty item apart from the wheels. The four of them sit firmly on the splines with virtually no rotational play, and they were all quite obviously out of round when they were recently checked on a balancing machine. In fact the operator did his best and was able to balance them a little better than they were. That was not a miracle fix though, and 500 miles later, including some on a few terrible roads, the dreaded vibrations were back.
I would be curious to know how heavy the Ace wheels supplied by MWS are. I ignore where the current wheels come from, but unless there were in the late 1990s more suppliers than MWS, they may well be from MWS already. I suppose I will order them a new set eventually, but I am still open to the idea of one piece alloy wheels that would reduce unsprung mass. The car may look odd then, but watching the wheels should not be a great concern when driving.