TBH the price you will get will depend on how long you are prepared to 'hold out', and if you wait long enough you will get what you are after. Supply & demand.
At 4.5k a ZS is A LOT of car for the money.
As for car tax... I know i'm not going to just fall over and stop driving the 180 just because the government wants £400 for tax. I pay that just to park my car for the year.