A lot depends on who employs you. Vistajet employ their crew directly and have agreed a flat untaxed rate of £35 daily subsistence allowance with HMRC, you get that in every country when you’re away from home regardless unless the company is covering the cost of your food. I don’t know what other companies do.
If you are working as a contractor you can use the HMRC subsistence allowance and pay yourself tax free up to that amount if you keep a record of where you were and for how long.
https://www.gov.uk/government/public...outside-the-uk