And then spend the difference in train fares. I'm 30 minutes outside london, an annual ticket is close to £4000.
And if I'm correct about where you live, the APCOA car park for that station is something ridiculous like 24 GBP per day.
And then there is what the time you spend on your commute is worth to you. If you decide to live >40 minutes outside, it starts to impact any social life you might want to have in central london.
Tip: you are not smarter then other buyers/renters. No offence but all the routes have been considered already. You always pay the price with time or money or lack of quality. Unless you work from home of course :).