Your plan needs the nest egg + house paid off. I will have 150k USD(100k GBP) by the time I'm 26 but no house. so i doubt I could survive a decade on it.
As you're alluding, half the battle with knowing when it is "safe" to hop off the treadmill is having a very good idea of your expenses. About 10 years ago, I spent a year or so recording how I spent my money to the cent. I found that it delivered a lot of freedom, even if I didn't live frugally, since it allowed me to know exactly how much money I would need going forward, and plan accordingly.
Since then. my life has changed a lot, to the point where the confidence in predicting my expenditure is wearing off. I'd describe it as a slightly panicked feeling of having to work harder, since I'm trying to cover the worst possible situation that my mind can invent. I probably should invest the time to collect another set of hard data...
Have you considered joining Mint, using plastic for your purchases, and considering cash as "already spent" expenses? (Stay out of debt, mind you -- use the cards as a way to ensure that it's accounted automatically.)
It probably does mean having housemates and being careful about where you choose to live, but it's imminently doable.