Complex sentence: Elvers, often fried, used to be a cheap dish in the United Kingdom, but, as across Europe, their numbers collapsed during the mid- 1990s; they are now not just a delicacy, but the UK's most expensive species.
Split into simpler sentences: Elvers, often fried, used to be a cheap dish in the United Kingdom; but, as across Europe, their numbers collapsed during the 1990s. They are now not just a delicacy, but the UK's most expensive species.