Also try http://www.workingintheuk.gov.uk for research. HSMP is something you (the candidate) will need to apply for before applying for an Entry Clearance (visa) to a British Consulate, whilst Work Permit is something your employer will need to apply on your behalf.

Upside to HSMP is that you can work for any employer anywhere in UK (or even open your own business or work as any jobs if you choose to) w/out anyone else needing to fill any further paperwork for you (hence it is more expensive - abt £400)

Work Permit is more like a British H1B visa - you can only work for the employer who has applied for your work permit.

Happy New Year!