Anyone got a good budget template for managing the finances of a self-build/extension?

[BobetteTheBuilder]

We have planning permission to add two big extensions to our home. DP will be doing most of the build himself, slow time, and we have a tight budget. I'll be shopping around for good materials prices, managing the finances and keeping a close eye on spending.

Has anyone been in a similar position and either devised, or found online, a really good spreadsheet layout for managing the budget? I'm thinking different aspects of the build on different tabs, with it all totting up on a master sheet. I could set one up from scratch, but am thinking why reinvent the wheel if there's already a good template out there.

Thank you!