Can I transfer TWES into Tier 2 ?

I am in UK since 2006, first 2 years on student visa and since Jan 2008 on TWES permit. My TWES is due for expiry on Jan 2013. I am receiving few job offers from different organisations but i want to know the options i have regarding my work permit. Can i transfer my TWES visa in to a work permit under any Tier categories?
Or if I can't transfer TWES into any other category at all, can i apply for Tier 2 from UK or my home country if the new employer is willing to sponsor me?
I'll be glad if some one clear my confusion.

Many Thanks

TWES is not a qualifying work permit category, hence you cannot switch to Tier 2 (General).

For you to change from TWES to Tier 2 (General), an employer must assign you a "restricted CoS" to enable you to apply for entry clearance as a Tier 2 migrant from your home country.

Thank you for the information
I know COS mean certificate of sponsorship but what mean by 'restricted COS', i was also reading this guidance but could'nt find the defination

Paragraph 62.