Since you have the York bars, have you checked the prices of Iron York 1 inch Plates? There are (or can be) as cheap as the OLY plates.
Do a Google price search.
These (the one in your pics) will work (and get you by for now), but personally, I would go for the Iron version rather than the plastic coated (cement, sand filled, etc) versions. IMO, the iron will take a more abuse and have a lower profile (width, etc), and allow for more weight on the DB bar.
EDIT:
For example, in the pics I posted, there is one with about 45 pounds and the other with about 40 pounds on the DB bar (the bar is about 5 pounds). And, I could put over 150 pounds on one DB Bar (3 25 pound plates on each side), as an example. Or 5 to 6 10 pound plates on each side.
I will only be lifting in me room so be on a carpet bare in mind. The thing is I need the dumbells to go to 20KG. With the iron york ones this will cost me a fair bit but the sand filled ones its £20 for the kit. I also need them aslittle as 7KG so I can do the the back lifting when you lean over and move the dumbell from your side upwards.
Im not sure if the iron ones will fit. Heres a picture of my dumbbell at the moment. (I do have 2)
If the look at the red bit you tighten and the weight there are little grooves but with the iron weights they dont have the groove but I guess this just means the weight will just spin around abit.