Wilkinson Sword Quattro Titanium Precision Blades x 8
INSTORE, scans nationwides (well at least Birmingham and Cardiff)
Works out ~75p each for a 4+1 blade system
The new (and unlike normal Wilkinson products incompatible) Hydro 3 and 5 systems are out (ok, better than the silly ones with wire guards, but not brilliant); appears Sainsburys are getting rid of the old Universal Blades. Given how cheap they are, I went back and brought another 8-pack. I'm sure the Titanium is the sharpest mainstream blade available.