Thanks everyone,
Our carpenter wrote a letter confirming he had worked on the house until the date of completion.
We've had a letter from HMRC today explaining they now have all the info they need and they will now process our claim within the 6 week timescale, once processed it will take 20 days to pay us. Does this mean we are now back down to the bottom of the pile and it's going to take another 10 months to get paid ðŸ˜
It's really annoying how they only gave us a few weeks to reply to their correspondence or our claim would be cancelled but they can work with indefinite timescales.