That's a tough one.
What's it worth as a going one?
Needing fixing 3 times previously doesn't speak well for the repairs.
You would have to wonder what else might be on the way out that isn't on the main board, but maybe nothing and they are correct that it will be better than new. £200 might be a good deal.
Still a fair chunk of change. Other deal where they keep it and give you £100 off something you fancy?