Hi Marsbar,
'Benefits' will vary from employer to employer and I'd also suggest that only the biggest corporates will have a very comprehensive list of benefits and the more senior of a level you are, the better the range of them. Some companies will give a smaller or minimal range of them, so there's nothing really consistent overall. Smaller companies will likely have less benefits, and given the current and potential future uncertainty etc, many companies are looking to reduce costs etc.
When it comes to Paid Time Off, then the minimum you'll find in the UK is 20 days per year. I can't remember if that's mandatory though. Again, depending on the company and perhaps the type of role you have, will determine the amount of days off you get. The HR and Payroll dept. will let you know how it's organised. Usually, you'll not hear of new employees negotiating how much holiday entitlement they can have, I'd say when or if it occurs, it'll be a very senior or executive management levels.
I've seen your other recent post about the potential move back to the UK and there's some good responses. Over the years on UKY, I've responded to quite a lot of similar threads to give the perspective I've gained when working in corporate, for USA Software/IT/Consultancies here in London and working with many many Americans who 'came over' via the company or by getting jobs here. Have a search on my username for threads with keywords like 'salary' and 'Cost of Living' etc and hopefully you'll see them to help you. I worked for 3 US companies in their London/UK offices and perhaps the most well known was Intuit, makers of Quicken and TurboTax and Quickbooks. The other two were a little more specialized and the consulting company had some very, very well paid employees (I wasn't one of those unfortunately!!). Without trying to bang my drum too much, I saw directly data which covered such aspects as income levels/salary related aspects, peoples thoughts as they moved over from the US, their thoughts after a few months etc giving me a bit of a unique insight into 'trends'. I have similar insight into those going from the UK to the USA and in addition to the 'work' and 'career' viewpoint, I also have my own family members, relatives and plenty of their acquaintances in similar scenarios, as well as some of my own friends too!
Personally, I'd say to stay in the US overall. This may be against the grain of the UKY forum members view of course but grounded in well reasoned thoughts and experience. Of course, I don't know your exact circumstances and like many who have already, moving to the UK may well be what you want/decide to do - which is fine as well, once you've evaluated everything carefully and properly!
Will keep an eye on your 'moving' thread and add some various aspects for you to consider.
Cheers, DtM! West London & Slough UK!