Hey ScubaSteve,
I will let someone else comment on the dental hygenist work, but I am an engineer, so I can comment a wee bit on that.
I moved to the UK almost 7 years ago for an engineering job on a work permit and I became a Chartered Mechanical Engineer a few years ago (background in plastics and biomedical engineering). I took a HUGE salary cut from what I had in the US. But my own
personal quality of life and standard of living is much much much better.
If you're wanting some good information about Mechanical Engineering in the UK, this page from the
Institute of Mechanical Engineers has a wealth of knowledge, including salaries,graduate schemes, finding vacancies, etc.
There is a good report on the
state of engineering in the UK as well, showing an overall rise in employment prospects. Not sure how much is extendable to non-EU citizens, however, I know that big oil-gas and power companies are always on the lookout for engineers (I see the jobs posted all the time on linked in) and these international companies are very atuned to employing people on visas.
If you can possibly do a graduate degree here, that could help your employment choices as well.
Good luck!