Another angle on this "I want 100k a year by X age" view...
There isn't really very much difference in lifestyle between 50k - 100k. The shift in tax means that of the extra £25k, you will only see around half of it anyway. And lets face it, if you're on £40-50k already, you're already in an income bracket where you don't have to worry too much about money. Those that earn minimum wage have to worry about the pennies when they're in the supermarket. For me, the biggest leap in quality of life money-wise came at the point I simply didn't have to worry about that sort of thing anymore. So if I see something I want to eat/drink, into the basket it goes. Same as worrying about MPG of my car, or whether I can afford to eat out overnight on holiday. The biggest leap anyone will make wealth-wise is simply not having to worry about cash everyday. Beyond that leap, there is no other leap until you reach the point where you have the supercar, 7 bed house with pool ect, at which point you can call yourself a rich bast@rd.
Earning effectively an extra £25k wouldn't really make very much difference. I would need to be earning substantially more to make my lifestyle 'better'. But on the other hand, for a spark, as has been pointed out, generally higher income means more hours, or in some way more stress and/or time away from home.
So at best you have a mildly wealthier lifestyle, but you get to enjoy far less of it one way or another.