No, you'd have to be earning an enormous amount to pay 50% tax in the UK. If you earn e.g. £150k, you get to keep £90k. Only £7000 of the money withheld is NI, so NI doesn't make that huge of a difference. Council tax isn't going to cost you £15,000 a year [1], so you're pretty clearly keeping more than 50%.

[1] If you're paying £15,000 a year in council tax, you must have some kind of gigantic property whose maintenance costs would dwarf that figure anyway.