Sean
I expect the Beach at Barnbougle would be fine for a person living in England. The water temperature will be fresh and bracing, compared to beaches on the east coast (Sydney and north to Brisbane). We have had people come here from Englans for work, and they have gone swimming in winter often, despite what we perceive as 'fresh' temperatures.
If you choose to visit, and make it to Adelaide, please IM me. Of course, the co-sanctioned event between the US Natiowide-Tour and the Australian Tour is on at Royal Adelaide in late February.
Peter Wood is right - if you know how, there are some very cheap flights about to get across to Barnbougle - similar to the way your Ryanair and EasiJet work.
The suggestion for March visits is also excellent - we call it 'Indian Summer' - temperature in the mid 20's, fine and sunny. Ideal for 'firm and 'fast' as the potential for severe heat sterss on the turf has gone, and many fairways are having irrigation reduced in preparation for the winter rains.
James B