hydrocracked mineral synthetic is still an improvement over the lesser grades, its just not as good as group 4 and 5 oils.
Some of the PAO and Ester based oils are blended with group 3 (hydrocracked) oil anyway, so even though it says PAO on the bottle its still not pure.
A lot of the rumors floating around about synthetic oils making old engines leak is down to early synthetic oils (like the original Mobil1 forumula) being pure PAO, as PAO has a tendancy to shrink rubber seals.
Most modern "proper" synthetic oils tend to be a blend of PAO and Esters, because esters tend to swell seals, and a balance between the two gives you no change. The lesser synthetics can be either a blend of hydrocracked oil and PAO/Ester types, or streight up hydrocracked oil for the cheapest stuff.
Pure PAO/Ester oil is likely to be 50quid or so a gallon, blended stuff somewhere in between and the hydrocracked stuff is what you get from halfords or your local motorfactors budget brand for 20quid.