Thanks for all the feedback. In the end I have taken the OTA saving. I think the chances of changes are slim, especially now that Thailand has announced no testing. The only problem could be with NZ if we test positive (assuming testing still required in October which I suspect it will be) but the Amex insurance covers £7.5k of changes due to curtailment I was told. So it seem Is can take that saved money and spend it on a hotel.