Hello firedance21c, I have looked into this trip and there are 30 people that have already booked with 10 places remaining. 22 of those 30 people are travelling from Heathrow, so an overwhelming majority.
As for visiting other places whilst on your holiday, you have complete freedom to go wherever you like, whenever you like. You are not committed to go on all of the excursions and tours that have been planned for you, and you can spend your time however you wish. This means that if you happen to travel near anywhere that is not part of the tour but close to the route, then feel free to visit.
I hope this information has been helpful and if you have any further queries then feel free to email me.
Kind regards
James, your editor