I have lived abroad and travelled quite widely too with family and alone. The major problem, now I am a widow. Is the exorbitant single supplement the companies want to charge for inferior rooms to. Drives me mad. I am perfectly happy to go anywhere and do my own thing. Have been travelling long before such things as trip advisor, and always did my own research.
As a lecturer and teacher am used to planning for all eventualities. So when a neighbour said she would like to visit Barcelona I came up with the proposal that we could go together. Share a twin room, therefore the cheaper price and better. But once there we do our own thing and behave as if we had gone alone, only having coffee together if it happened to suit.Pay your own bills etc.
We agreed and it worked very well. We shared one coffee and one meal over the total time, and have done this kind of trip in Britain with others. You have to be very clear in your planning meeting, about all sorts of things, from what time you get up and how you like to start your day etc. Whatever is important for you. So I couldn't take a trip with asmoker, but if someone starts their day with 4 cream cakes, that is up to them. I tried to get the NT, to have a contact list, where you could share the cost of travelling to properties, but they wouldn't play ball. So I would suggest that you start by looking at groups that you already belong to as away of experimenting. So if you are in a gardening club. Maybe you could suggest a trip to Cornwall to see 2 or 3 special places that don't have good access by public transport. When I do this, I propose that I will drive and we start with full tank. And then furled costs are shared by all. Food on the way whatever suits, a kitty. Or buy your own. And no stupid. Let me buy these etc. Then there are always too many places to choose from, so usually quote one or two definite places we all can visit together, the rest negotiated. For evenings, you either work independently or may agree to minimum phone call to confirm everyone's OK, or just be responsible for yourself.
Always worth trying out a couple of nights, to check how wellyou get on.
Then you can graduate to morespecial trips abroad. Also , in the case of cruises, where there are few single cabins. Ask them if they have a same sex dormitory, or shared cabins for women etc. You can also look at university holiday spaces. Good for places like Cambridge. But I just decide to go somewhere and then see what there is on offer. I am 80 now and still travel. Go with a good heart and a willingness to learn and you will have a great time.