Not a good idea, either.
I know the idea of mixing has a certain appeal, but trust me, you and the animals wil be much better off avoiding mixing, it´s all unnecessary risks and no benefits.
I see you have guppies in the water. Although they are not necessarily a problem, beware of the fact that newts can chemically sense fish in the water, and some individiduals may not like that at all and avoid the water. In the wild they actively inhabit fishless waters.
I would also like to recommend that you use a lot more live plants in the water area, they simply love them!!!!! They trully have a strong preference for very densely planted areas.
As for the breeders, it´s certainly not easy to find local breeders, but they needn´t be local. You are lucky, the UK has many, many excellent breeders who will be able to ship the animals to you. This sounds worse than it actually is. Most of us had the majority of our animals shipped to us, and for the most part, there are no problems if things are done properly.
Petshop newts are all wild caught which is a big problem not just for the poor animals, but for you as well since you will be purchasing extremely stressed, possibly ill or starving animals that may die shortly after being purchased or require a long recovery.