Weren't sure if you were 'Old School' or not, Lol! Glad to hear 'not'.
For treats I use Gerber's Graduate Puffs. There's about 400 in each container and only cost $2.00. Little cracker like things. Don't know if you can get them across the pond though. Plus they're low fat, low calorie, low everything come to think of it, so very good for lots of training without filling them up. Maybe you can find something similar in human baby/toddler foods over there. Plus they make many flavors or the pups don't get bored. Mine are partial to blueberry, peach, sweet potato, and apple flavors. Natural flavors.
Most dog treats I find here are so expensive, or give my dogs diarrhea, way high in fat and protein, so after 2-3 treats they walk away. I stay away from high sugar, fat, and sodium content, but no sugar free stuff, artificial sweetners are not good for dogs, or humans for that matter.
Oh and I did see your Yorkie Restroom.... excellent idea and very creative! Love your sense of humor... lol.
Some folks are 'clicker' training their dogs with great success... I just use a well timed 'Good dog'... I think it does the same thing. Trainers: Correct me if I am wrong.