Many of us, and/or our partner also work 100 hours a week, rarely see their children, in dull jobs, for which they work their bollocks off, for which they have studied hard blah di blah ...... and all for a wage considerably less than you must be on. In fact, for a gross wage, before tax, which is very much less than the tax bill you are moaning about.
These people don't have the option of working less hours because a drop in income would mean they wouldn't be able to live.
If you are able to turn down jobs purely on the basis that they are "dull" (and not because they don't pay a living wage) then you are indeed very fortunate and, if you are for real, your complaints are astonishingly selfish and tactless.
We all live in this society and all have tax obligations. These go up and down as our incomes do. But it would seem very probable that you have far more flexibility so far as choosing what you do than most. If not seeing your children bugs you that much, then cut your hours (if you are paying £72k p.a. tax then I'm sure that wouldn't be impossible) but no, that, apparently would be "dull". Perhaps spending time with your children isn't actually that important to you after all if "dullness" at work prevents you from making that change.
Anyone who defends their good fortune as being the result of them "working hard" really gets my back up because such a statement implies that those who aren't in such a fortunate position haven't worked hard .... which is, of course, a load of tosh. High earners may well work hard, but there will also invariably be other factors involved in their earning capability, such as having a supportive family when they were getting their qualifications, such as having the natural "luck" to be born with an aptitude for particularly well-paid professions, such as being in the right place at the right time, such as living in a location within commutable reach of well-paid work, such as having a great childcare support network (to enable work and/or travel, and/or long hours) ..... and 1001 other permutations which all add up to someone achieving financial success at work.
I would guess (not wanting to put words in Twig's mouth) that that is what she meant when she said you were fortunate, because, somehow, somewhere along the line, it has all come together for you, and people in a similar position to yourself. (The same can't be said for everyone - no matter how much they put in and how many sacrifices they've made). Okay - your life isn't exactly as you'd like it, but whose is .... and I'd hazard a guess that financial security (which you appear to have) would be pretty high, if not at the top, of most families' wish list, particularly in the current economic climate.
No-one likes taxes but they are a fact of life in a civilised society. Those lucky enough (see definition above) to earn a much higher than average wage should pay a higher rate of tax .... and remember that that 40% rate also applies to people earning much less than you, who are deemed, at least in the government's eyes, to be in a "fortunate" position as well - hence the higher demands upon their wage. Would you really insist you're not "fortunate" (in the salary respect) when compared to another 40% taxpayer earning just over the threshold (£39k-ish IIRC) ?? ...... who also works long hours etc etc etc.
Think yourself lucky you aren't living in the early 1970s when the top rate of income tax was 83% .........
Oh .... and whether or not you pay a 10% tithe to the church is irrelevant to the taxation issue. How you spend your disposable income is up to you and has no bearing upon your obligations to society as a whole. The church - or any other charitable organisation to whom an individual donates - then spends that money on specific projects. The tax we pay goes into central coffers which (in theory) benefits everyone in one way or another.
So .... the short answer is a resounding, YES, you are being very unreasonable to complain, and staggeringly insensitive.