The HMX-W300 has a maximum optical sensor size of 1/3". That's 4% less optical sensor size than the most common optical sensor size of 1/2.88". 4.80 x 3.60mm. Across all similar spec camcorders that have been available for more than two years the optical sensor size ranges from 2/3" (worst) to 1/1.3" (best).
It may also be worth considering one of the other video cameras that have a 1/1.3" optical sensor size currently available including because of it's better review score, the Canon XF105 (£1,729.00).