This is going to really test me as I'm not very organised at the best of times - ok at keeping lists and records but not so good at putting it all together accurately iyswim.
Suggestions so far:
Move the money for the project into one single bank account, use that to pay the builder and always use the same card for purchases so it's all coming from the one account.
Get a long term 0% credit card and leave the money in usual accounts earning (small but adds up) interest. Just pay off the minimum each month and pay the balance at the very end of the 0% term.
Excel spreadsheet for the builder costs recording what's paid and reducing the balance due
Excel spreadsheet for non builder costs like kitchen and flooring, showing the budget of estimated costs of items and then actual costs as they are made.
Any more tips, please?