I suspect it wasn't your tour operator that went bust but the airline that they'd chartered to fly you to and from Tunisia. The Irish charter airline, TransAer ceased trading in October 2000, leaving customers of the companies who'd chartered their planes temporarily stranded overseas.
Alternatively you might have booked with Fly The World Travel Ltd, who were based in Ashford and who sold holidays under various brand names (so it might not have been 'Fly The World' which appeared on your paperwork), as they also went bust in October 2000.
They were the only two business failures to make the pages of the weekly Travel Trade Gazette that month. Fly The World collapsed near to the beginning of the month (with the news being printed in the TTG issue published on the 9th), with TransAer going under nearer to the end of the month (with the news appearing in the TTG issue published on the 30th).