I've always worked in IT. Whilst I don't quite earn £400 an hour, I do alright. Enough to have to be well in the 40% tax band that is.
Years ago i was an IT contractor and was earning about £8k a month for pretty much a 9-5 job. I was about 27 at the time. Alas, those days are long behind me since after two kids & a mortgage I opted for the relative safety of a permanent job.
I get to work from home and have travelled to more countries than I can remember all on expenses. Some companies even flew my OH out for a weekend to join me since it was cheaper to do that than pay for me to come home.
A guy I work with sometimes in another office, whom is relatively junior but is a nice enough lad has just been offered £35k job. It's not even difficult and like I said he's a nice lad but on a geek scale of 1-10, he's probably a 4 if I am generous.
Experienced IT project managers are usually on £40k+ at least. More if you are down south. Programme managers can command six figures. Most probably couldn't turn a computer on, such is their level of knowledge.
As for barriers to entry then it is like most industries, hard to get that first break. Once you do though, really the sky is the limit. What I'd say though is unless you have a passion for all things gadgety, don't be a techie. You will hate it. Go be a project manager, service manager, whatever. You can still earn good money. If you love tinkering with computers, like me who is currently spending his spare time typing on MN whilst setting up a couple of servers just to learn then a technical route is still a good bet.
Just avoid working in a call centre unless you can see a route out.