Going around the Greek islands used to be a favourite! However long haul for s shorter time gives fewer options in September. South Africa isn’t expensive. Flights are but it’s spring there and the whales can be seen at Hermanus.
Far East? Thailand, Cambodia? Vietnam? Laos? Vietnam has the advantage of being visa free for British citizens if your stay is 15 days or fewer. September is just starting to come out of the wet season for some places, so may be some good deals to be had.
DS and his bestie went to Peru last year for a month. They had a great time, but a month was too long. They did a mix of hostels/bit of camping/nice hotels. They want a cheaper trip this year and so are thinking of going away for 10days or 14.
Where is good long haul in September?
They want to avoid USA as DS isn’t old enough to drink there.