Hey Chlozo,
What it sounds like you want to do is sell templates?
If you want to set up your own site then you need some form of server-side language(PHP/ASP.Net/Coldfusion) running the back-end... Or you could use someone else's services (e.g. paypal[google there are many others]).
You'll also need a webhost to host the main site, you could use a freehost but usually you have to agree to the site's advertising terms. Yet again, google is your friend.
As for tutorials, they're hard to find, google again, i found one here:
http://www.davesite.com/webstation/html/domain.shtml
Though i've found one here:
http://www.w3schools.com/hosting/default.asp
and i always trust w3schools and the information they provide so i highly suggest it (without having yet read it)...
The problem with what you want to do is it is template based, if you want real work look into joining some form of web-design firm (jobsearches online tend to be good with that[finding one near you])... You'll also find that there's a tonne of competition in the UK because there's too many of us to go around.
Still it should be enough to help save for uni(something i'm currently doing =[)...
Post back for more info.
Cheers,
Jamey
p.s. if you're midlands based then post back saying so and i may be able to suggest somewhere near you... I know of a few web-design firms which may take you on, but i can't remember the names and i can find them for you if you want.