Jurajk, the store probably has a large inventory of PQ Universal. The main difference in the two developers is image tone.
Download the .pdf files on B&W Paper Developers from Ilford: http://www.ilford.com/html/us_englis...rdeveloper.pdf
Ilford sells three concentrated liquid paper developers:
1. Ilford Multigrade Developer, a "Slightly Neutral Tone of Image" Dimezone-S/Hydroquinone developer.
2. Ilford PQ Universal Developer, a "Slightly Warm of Neutral Tone of Image" Dimezone-S/Hydroquinone developer.
3. Ilford Bromphen Developer, less concentrated than the previous two, a "Slightly Warm of Neutral Tone of Image" Phenidone/Hydroquinone developer.
Since Dimezone-S is one of the Phenidone developing agents, all three of these developers are PQ developers.
I have been mixing PQ Universal "from scratch" (I use Phenidone - not Dimezone-S) for many years. It is easy to turn it into a neutral-cold image tone developer by adding benzotriazole (start by adding 1 gram per liter of the working solution). The resulting developer gives results very similar to Dektol's, but the image "comes up" a little faster.