Thanks for this Tris, I wonder if sunshine is one factor as I have Sungold tasting superior where grown against a south-facing wall – but also the plants are in bags of soil with less access to water, and the fruit are smaller. Did you perhaps water less at the allotment? Soil differences also are surely playing a psrt.
As with so much in gardening, it is hard to isolate precise causes, but one can make interesting suggestions!