Having been on CX PE 10+ times, its much more comfortable and have better sleep then Y class. The only thing I dislike its when the person infront recline their seat, the inside passenger have difficulty getting out also I can't really stand up with too. Like others you should consider the the hard products rather then soft.
Since a glass a champagne (5 pound)
-hot towel (5 pound, if you ask me its worth nothing)
-better meals (10 pound),
-priorty boarding and getting off (10 minutes?)
-bottle water (2 pound)
-amenity kit (5 pound which I often giving it away since I got stacks from variety of airlines)
-head phone (I don't know how to price that since I have my own noise cancellation headphone, maybe 10 pound)
-extra 5KG (worth it if you use it since CX charge extra luggage KG cost a lot and heard recently they are really strict)

The extra price is upto your own preference, I would only pay about 300 pounds or up to 40% more the economy. Since CX Y class is one of the best out there especially their 777 (9 across 32inch). Part of increase of price are due to UK APD an extra 70-80 pound.

Just curious when did CX start both serve both meals from J for PE? that wasn't the case when I last travel last year. Which route would that be? Since when?