Alan's guidance on this has served me well; until more recent experimentation with 510-Pyro, I have routinely used Perceptol 1+2 for HP5, even at box speed.
You will never get fully satisfactory results until or unless you develop your own film, and find a good scanner. JPEGs from AW will never give you optimum results.
You can push or pull HP5, as long as you appropriately adjust development times, for which there is clear guidance widely available, including in Ilford's own instruction leaflets.