I've got a decent 206 2.0 HDi for sale....why go for the 306 when you can have all the toys, cheaper tax and less weight. 
But as for the engine, the actual block/head is the same as the 306 but there are other differences. Depends whats actually broken and how much needs swapping....

But as for the engine, the actual block/head is the same as the 306 but there are other differences. Depends whats actually broken and how much needs swapping....