Sounds like you have a healthy income to set aside for the works @BedHelen , however I totally agree with everyone saying that building materials and labour costs have risen dramatically over the past few years. Having a good idea of your proposed budget is great, but it will inevitably cost more. The only reason we've ever come in under budget is because of the sheer amount we do ourselves. But that can take years!
We took on a 3500 sq ft project house when we were a bit younger (30/31) with one DC (7 yrs old). It had been converted from a six bed to several flats in the 1960s with very little done since. Learning along the way we DIYed as much as we could including all plastering, tiling, fitting kitchen, 2 x bathrooms/2 cloaks etc, rebuilt victorian conservatory, landscaping etc. The whole process took 8+ years. Had new roof, heating system, rewire etc all professionally done and spent a total of around 100k back then (early noughties). God knows what it would cost now.
After that in 2012 we added a - mostly self-build - large, vaulted-ceiling kitchen extension to a different house. Our architect said it would cost 25k. Came in at 45k.
Our last (much smaller, but fairly major as we reconfigured whole floor plan) reno was done pre/post pandemic and the cost of everything skyrocketed during the project.
Nonetheless, we completed it for 80k and took on another in 2024. Budgeted 50k to do kitchen, bathroom and lootility, heating (boiler was from 1980s, no longer working), integral garage conversion (was originally part of the Georgian property), remove a couple of walls, add a wood burner.
We're currently half way through and have spent around 20k, but we can now DIY almost everything (except gas safe/hetas stuff) so the savings on labour are enormous. We also shop around to source high end fixtures for bargain prices on the likes of eBay etc.
I'd not discourage you, but go in with the expectation that it'll cost at least double your projections.