The wet belt is nothing more than a cambelt in a casette that runs in oil.
Ford replaced the old lower chain that used to come on the Lynx diesels with a belt to improve emmisions and fuel economy. I believe it was fitted on all 1.8TDCi's from 10/07 onwards. Ford say that the interval is 125k/10 years but I've heard of a fair few failing at just over 90k.
Older Chain...


Newer Belt (fitted 10/07 onwards)...


And then you obviously have the usual cambelt...


A huge chunk of the cost of getting it replaced is the amount of bolts, seals and gaskets that need replacing.
I paid £620 at a main dealer but that included a bit of discount and a tank of diesel as I was messed about a lot.