Seeking employment

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That's the problem: you're on the YMSV. No one will hire you in your field while you are on that. You'll be better off getting something in the hospitality industry to get you by. They a) want someone who is local, b) someone who is from Europe, c) someone who is a permanent resident of the UK or Europe, d) someone with UK experience, or e) some mix of the above. The stigma of the YMSV is that of transience.

Taken directly from the UK Border Agency site under the YMSV:

Settlement

This page explains how there is no right to apply to live permanently in the United Kingdom (known as 'settlement' or 'indefinite leave to remain') if you are here under the youth mobility scheme under tier 5 of the points-based system.
You cannot apply for settlement from tier 5 and the time you spend in any tier 5 category will not count towards any settlement you may apply for in the future.

Besides; you have to leave before your visa expires, no ifs, ands or buts, according to all of the literature.

If you have a bachelors degree, you can apply for the Tier 2 visa, as long as you can get a sponsor. This has to be done outside of the UK; there are no transfers to other visas.

If you have a masters degree (they may have relaxed this), you can apply for the Tier 1 and apply freely. I'm not sure if you're allowed to be in the UK or not for this one.