I think this is the second thread I have started on here in regard of getting another dog.
I am an experienced border collie owner. They were the dogs we grew up with as children and when I got my own flat aged 18, I adopted a border collie lurcher from a very reputable rescue organisation. She had lots of problems. She had been an unclaimed stray and had been rehomed several times before she came to me. She was quite wild, an escape artist who never really was allowed off the lead. She would unlock the doors and get out of the house, open cupboards/the fridge etc. She was the kind of dog that was hard work and I don't think many people would have put up with her for very long. She was dominant and didn't like men getting near me. The list is endless really, but I worked really hard with her and she became an absolutely wonderful family pet and when I had children she was absolutely golden with them. Unfortunately just over 12 months ago at the age of 17/18 I had to have her put to sleep :( In the meantime of having this dog I got another rescue dog from Wales, another border collie, this one is now 10yo. She is a completely different dog, a bit on the nervous side but very loving, loves walking long distances but isn't playful in the same way the other dog was, but is almost a perfect family pet, wont mess in the house etc and you can really trust her.
Anyway. I have been looking at other dogs on rescue organisation websites etc and I haven't seen any suitable but the other day one came up that I thought would be ideal so I applied and they rang me, seemed keen etc and I went to see him and they said I could reserve him but the other dog had to get on with him, which I agree is important. So I took the other dog along and we got half an hour locked in a compound/grassed area and they then decided the other dog was too boisterous for my dog. My dog is extremely well trained though and isn't a dog that will run in a field unless you are walking through it iykwim If I stand still she will sit next to me looking at me. If we are with strangers she will stay at hell and walk behind but this was why they didn't think the dogs were suited together, yet I felt that with the right training the other dog could be quickly sorted out and make a good family pet for us. Instead they suggested another more difficult dog, with lots of problems because I was an experienced border collie owner 
I don't know what to do now. I feel really disappointed, obviously. I don't know whether to just knock the whole idea on the head and just have the dog I have as a single dog. She just seems so lonely though as a single.
Thanks for letting me offload