Hi Shaz,
I've just done one tour with TS and I know some JY folks have done a number of TS tours, so they might be in a better position to answer. I think the best way to answer your question is that if the meal is included, then people will be eating together, but if the meal isn't included, people just do their own thing. If there were a number of single travellers on a TS tour, I'd say they would probably arrange to meet up and of course if I was the only single traveller, I'd probably try not to be shy and ask some of the others if they minded me tagging along. There are a couple of reviews of TS tours - see also my one on the S America tour I did in 2012 (Chile, Argentina and Brazil) as it might give you a fuller flavour of what I mean. On my tour (which I thoroughly enjoyed), I was given a double room throughout. As far as I know most hotels outside Europe only have double/twin rooms - in older/smaller hotels in Europe some do have single rooms, so it depends on what the hotel allocates. Hope this helps!
Cheers,
Bob