Re: US or UK???
1-Plenty provided you are WILLING to work. A lot of pakis complain about lack of employment etc.. it's usually because they want their dream job after graduation. If you have the skills, ambition you can get a good career
2- Everything is fairly expensive. Having said that £25k outside london will let you do most things comfortably.
3-I dont particularly like the lifestyle. Plenty of hard work with less play. Traditional evening is out in the pub. I usually end up watching TV or something as lack of things to do, unlike Pakistan.
4- Can be done if you want. Not much bureaucracy but businessmen will always complain about the paperwork. Tax's are fairly high compared to US, PK. Compared to rest of Europe lower.