"actively exploring exits" is not the same as "rush to sell". Most startups are actively exploring exits as that's the whole damn point of a startup

I’m expecting changes to CGT, gambling winnings, pensions for higher (and up) tax rate payers, and IHT

I’d guess the pensions makes sense - you can take money out of an effective 62% tax rate, but you’ll never be paying that sort of tax rate when you withdraw from your pension, so that tax just wouldn’t get paid

IHT has so many exemptions too. The tories would have done better just having a simple system and increasing the threshold. Right now, you can pass a pension down and it’s exempt from IHT, and you already skipped a bunch of tax on it already

UK IHT threshold relatively recently, would increase each year, until 2009 and it’s been static since, if accounting for inflation it should now be £500k instead of £325k

Business Asset Disposal Relief (previously known as Entrepreneurs’ Relief) at 10% (20% if £1m+) may seem like a sweet deal, but if the worth of your business is its balance sheet, then you’ve already paid corporation tax at 25% so the effective rate is 32.5% (40% if over £1m). The gov has little to no wriggle room before it’s not worth taking the risk of incorporation.

If a startup is making money, why sell?

Because often a payout and money in your pocket is worth more to you than the years of uncertainty

If someone offers you cash today to buy something which either might go up or down in value, many people will take the cash

But if people are selling because it will go down in value, the buyers know that too and bid less. The traded price will always be (approximately) one that makes you indifferent to buy or sell.