Yeah that’s normal in Britain for council and government fines (as opposed to often unenforceable private parking charges). The shitty part is that if you try to dispute it they don’t put the timer on hold so you essentially play double or nothing on how strong you think your case is. Lose and you have to pay the full thing. Not bitter at all.
Normal to get a 50% discount for paying quickly and without appeal. Last I checked you couldn’t pay with Nectar points, though.