Quitting a job within a year won't look particularly bad on your resume; quitting multiple jobs within a year will, however. I left my first job after 3 months and I've never faced a problem because of it.
There's no need to berate him on his English, especially if he's moving to London - as long as it's clear that English isn't his first language, or that he's dyslexic, then he won't be judged harshly there.
There's no point sticking with a job you hate if you have the means and freedom to move on. Being young allows you to change your mind before too much depends on you having a stable job.
@op: Look up on what's currently in demand in London (Java, probably) and start learning in your spare time. Check up on a few UK-based recruitment websites (http://reed.co.uk has a good list of programming jobs). It's totally possible to change your area of expertise; I currently work as a Ruby/PHP developer and I have a first-class degree in design :)