Holiday 28 days minimum - as per law https://www.gov.uk/holiday-entitlement-rights/entitlement
Rarely offered health care but - for all its flaws - our National Health Service is pretty good.
Shares - yup, they're almost always going to be worthless.
Pension - every company has offered me at least 5% matched pension - some more. The Government is mandating that even small employers will have to put you in a pension scheme soon - which is good.
"Soft" benefits like gym membership / conferences / etc depend very much on how confident the business is in itself. If it can afford them, it likely will - because they know that people can get them at mega-corps.
Pay - ah, there's the kicker. Yes, most startups try to save on the salary costs. Usually they get a pretty rude awakening when they try to hire someone with more than 5 minutes' experience. So they try to make it better with "up-titling". I could have been "Global Head of X" at a company barely looking at sales outside the city.
Joining a start-up is fun. But, like a pyramid scheme, you've got to get in early if you want to reap the share bonanza benefits.
I do wonder why the UK scene doesn't seem quite so vibrant - especially as healthcare costs (which I understand to be the biggest burden in the US) are essentially nil.