So flying B1900 on an FAA licence that you'll have to convert to?
Not sure how much help it will be for keeping your JAR licence current and getting back to the UK.
Honestly as a gamble, Lion Air ought to be more attractive as a P2f to me if you really must do it but personally I'd go with the instructor route in Australia/New Zealand. Lots of growth going on in that part of the world and you'll have a great time and then with bit of effort you'd get yourself into something similar for a lot less money.