I was put through to the Philipines, and they quickly put me through to UK Retentions.
Changed to the "unlimited" VIP £15 tariff with no qualms at all. £5 Sim fee refunded as he said it was an unecessary charge, and this month's bill reduced by £2 to bring it in line with the VIP tariff.
I was told there was a lot of confusion over the new tariffs!!