How much notice to terminate a commercial lease?

I realise this is more law than accountancy, but wonder if anyone can help?

A hairdresser pays rent on her salon on a weekly basis.  She signed a 3 year lease in 2006 and has signed nothing since.

She now wants to leave at the end of this month.

Is there a statutory notice period she must give and pay full rent for?

Can the landlady evict her as soon as she tells her she is leaving or must she give notice to do so as well?

I can't find a definitive answer on the web and would be grateful of any advice please ...............