Yes, that's a really tricky situation.
We have had at least 4 conversions nearby over the last year or so.
The noise is awful, and I have 3 little ones to get to sleep in the afternoons, BUT, like someone else said, the WORST of the noise is over in about 3 weeks, and after that you dont hear much at all.
Perhaps if you also explain this to your poorly neighbour, he will know that there is an end to it. If you know it WILL be quieter very soon, it wont drive you so crazy!
Anyway, it's only done once, and once it's done you can have them round and spoil them with dinner etc to placate?!