Has anyone had to deal with this when extending??

[extentionmadness]

We're having a fairly reasonable (we think) rear single story extension on semi-detatched property.

Originally we planned and have got planning permission to go right up to boundary, but we've brought it in a bit as neighbour clearly wasn't happy.

I've noticed that the surveyor chosen by them is a right of light specialist. Has anyone come across this before or know anything about it? I've read that they can get compensation/injunct the build if there is an injury.

Neighbour is not talking to us so we're trying to second guess everything and don't want a legal dispute.

A friend ended up having an extension with the corner cut off (with French doors on the diagonal) which looked fab. I complimented her on it and she said it was because her neighbour kicked off about right of light so they changed the design.

There is no legal right to light. Or a view.
If you have planning permission your neighbours should have been consulted and the impact on their property would have been taken into account. Get a copy of the planning officers and/or committee report.
If you change your design you will need to reapply for planning permission. If it's minor i think you can apply for a minor alteration otherwise it's the whole process again.