Thanks for your support. I should add that I'm retired and no longer interested in resuming my teaching career. I should also stress that anyone breaking the visa regs while working in the public education sector should do so in the knowledge that there's always the (slight) risk of being caught doing so by immigration, and having to face punishment as a result thereof. It's therefore advisable to have sufficient funds available to pay a substantial fine and purchase a one-way air ticket to your homeland at short notice.