After the brief run around the yard, it became quite obvious that I would need a cooling fan. In fact, I had pre-empted this requirement and run wires to a dashboard switch.
A quick browse on ebay and I am now the proud owner of a 12" fan that (importantly) draws less than 8A so I can run it without a relay.
Fitting was simple;  nosecone off, fan fitted, fan wired, tested, and nose cone back on. It even passed a "live" test while running the engine. Job done!