I am involved in rottie rescue and see literally thousands.
I am UK too so I can help you actually locate one and I can tell you what to look for. Go on Champdogs or Rottweilers Direct and start there.
Do not go for a petstore dog for goodness sake. They are very badly bred byb dogs selling for over the price of a well bred health tested dog. So that's that out for a start.
Try to look for someone that has fully health tested their dam and used a sire that has also been tested. You might not be interested in a show winning sire and dam however these tend to be the healthiest dogs and therefore produce the healthiest pups. Just to help you decide on that a friend of mine has just spent £12,000 on her pup who was so genetically F...d up that his spine was crumbling. Another of my rescues found in a box on a train station has just been diagnosed with joint problems and is going to need operations.
You have to be very careful with rotties as although a lot you see are purebreds they are often badly bred, and our breed can suffer with so many things such as HD, ED, OCD, entropian, pano and other genetic problems that is wise to spend a bit more money now.
Always get a rottie insured as well. I rarely get away without spending £1000's on a dog in it's lifetime on veterinary. My b*tch in the avatar has just had vet bills totalling £900 but I am insured.
Always always go to someone who will ALWAYS take their dog back at any point in its life, as so many people find out that when the breeder doesn't take back and they ring a rescue expecting them to take it, they find every rescue full up, and no alternative but to put a young healthy dog to sleep.
Can I also ask -- are you really ready and experienced enough for a rottie and is your situation stable enough to know you can offer the next 10 yrs to this.
I have no problem in you emailing me ANY questions regarding the breed. I would also be honest if I didn't think I would allow you a dog if it was me homechecking (which is what I do for rescue) got one this afternoon and another tomorrow morning in Southampton.
That sounds hard, but lets just take yesterday. I drove the 50 miles there and 50 miles back to go to our rescue kennels and it took me 3 hours to walk the dogs we have in. So 5 hours of my time, and 100 miles of my petrol money to walk our dogs. This happens day in day out that someone has to go.
So I don't want people owning our breed that cannot commit to it 100%..