The problem is that this is a new build property and this will invariably be covered in the terms of the contract absolving the developer of any liability for late completion.
What usually happens is that completion is triggered with a valid NHBC or similar certificate and the seller giving notice to the buyer formally.
Unlike a normal residential purchase, where at exchange, completion date is agreed in most cases, for a new build, it’s common to exchange often on a greenfield with completion at some indefinite period in the future. Usually, in the contract, there will be a long stop date to allow a get out if the matter is going on for years..
It is the seller that drives the completion date but it has to be formal notice, not just an estimate.
So to answer your question completely, it would be necessary to see the terms of the contract.
It is highly likely that you would have no right to compensation. Depending on the terms of the contract, you may be able to withdraw but it is unlikely.
I’m sorry, I wish I could give you better use but it’s one of the problems with newbuild delays. It is quite common.
Incidentally, if you have been trying to get hold of your solicitor today, Friday is never a good day because the majority of completions take place on Friday so that people can move over the weekend.
Can I clarify anything for you?