Objecting to neighbour's extension?

[FondOfOwls]

Sorry, not sure if it's the best place to post it.
We received a letter that our next door neighbours are building an extension. Overall I have no problem with this, but noticed they are planning on getting their balcony more than twice as large as it is, and I am worried they will have a very good view of the whole of our garden like this, thus resulting in it being less private.
They didn't mention their plans before and I am not sure how I feel about it, I'd rather they didn't make their balcony so huge, but we are friendly with them and I'd rather keep it that way. I was thinking about just objecting to it, but if it gets ahead anyway I'd rather not ruin our relationship. Then gain, they could have mentioned their plans before! Does anyone have similar experiences?

Are you able to have a friendly chat with them about it and express your concerns? Possibly the potential effect on you hasn't occurred to them. Or it may be that they could allay your worries by showing you that the balcony won't overlook to the extent you think it would. You could present this as your trying to see if they'd be willing to modify their plans before you send in your objection - perhaps they won't be, but at least it won't come as a shock to them when you do object and they might be a bit more understanding of your reasons.