G'day! Welcome to Cheftalk.
Not all of the members here are chefs, I'm not - just an enthusiastic amateur - but I DO live in the UK.
If you are an Australian, you should find it relatively easy to get a working visa IF we are looking for chefs in our migrant workers. You should check on the Borders Agency part of the Home Office site - which has all the info regarding work permits/visas for the UK. http://www.ukba.homeoffice.gov.uk/
If you are not an Australian, and not a national of either a commonwealth or a European nation - then it would be more difficult to get a visa.
I would also urge caution regarding use of many of the websites which promise you a visa..... particularly those emanating from countries from where we take few nationals, but who promise students the earth! (I know, from the experience of some of my overseas students who used agents and were sold a 'pup')