isallshit - haven't read all the posts but wanted to say sorry you feel so lonely.
There have been many great suggestions as to how to get out and about a bit more, and I wanted to add a few of my own that have helped me.
I live in the Midlands, but not near family or old friends, my DC are away at Uni, my H left 8 months ago and I am trying to rebuild my life.
I have a part time job and that leaves many hours to fill, but I would like to work full time.
I walk everyday, just being outside feels great, I also do something in the garden most days, I am lucky to be able to go to the gym. The exercise, of any kind, and especially the 'free' kind, is good for your natural feel good hormones, endorphines (sp.?).
I don't know if you drive or live in town but if you can then Waterstones run book groups.
I am the 'wrong side of 40' too, there is a group in the midlands called 'friends around 40' (I think), they have a website, they organise walks and trips.
I have been, by myself, to the theatre and museums. On a sunny day I sit at cafes with a magazine or book and a glass of wine, watch the world go by.
I have done the dancing thing too, and believe me, there are many shapes and sizes there, not every one is lithe and beautiful.
It is good to be out of the house and around other people, even though you are not engaged in conversation, it does make you feel less isolated.
Hope all of this and what others have suggested helps.