I have news for you. Lighter does not equal better. The Type 23 is a decent frigate. No one with any credibility has ever argued it's a bad frigate because it's larger than other frigates. Just as the Type 31 won't be bad because it's bigger than other frigates.OK so you don't know what countries are getting even lighter models like MEKO2000; Daewooo DF- and DW-; Sigma; Gowind
Also, and I'm surprised you don't understand this, the bigger the ship the more flexible it is, because it can have a wider array of mission modules and equipment. Steel is cheap, so the cost of making a ship larger is not that great. Of course there comes a point where you're wasting money because there's no significant benefit. But I think the Type 31's estimated displacement is fine. A bit more than the Type 23, but not a lot. Still a general-purpose frigate. And obviously less than the Type 26 (which is still called a frigate).