Pyro is indicative of a chemical formulation utilizing either Pyrogallic acid or Cathecol.
Originally Posted by Snapper
The reason to use one of these classes of developers is 1. Increased sharpeness due to adjacency effects. 2. Proportional stain...that is stain is greater in high silver density regions of the negative. This increases hightlight tonal separation. 3. Ability to build higher density range (contrast) in the negative. This is important to photographers who work in alt process or Azo.
While most black and white films will benefit from pyro development, the films that benefit the greatest (due to the ability to expand contrast) from pyro appear to be Tmax 400, FP4+, Efke PL 100.
It isn't difficult to use. There are important safeguards that are encouraged. Those are the use of a respirator when mixing powders and the use of gloves to eliminate hand contact with the liquid developer.
I am not certain about the UK. I buy my chemicals from Artcraft and mix the developer from the individual ingredient chemicals. Artcraft and Photographers Formulary both sell kits in which the appropriate chemicals are already formulated.