The UK proposal will not allow using works merely because the author is not explicitly identified. A diligent search must be made Furthermore a fee (royalty) will have to be paid to a government administrator and will be held in case the author eventually comes forward.

From the horse's mouth:

Having considered responses to the consultation, the Government’s intentions are as follows:
• Diligent search before something can be used as an orphan work is key to the scheme. The Government believes that it is important to strike the right balance between a relaxed standard of diligence and for an “awaiting claim” approach, as against ensuring that absent rights owners’ needs are protected. The Government is mindful of the need to ensure the process is sufficiently straightforward to be useful to potential users. The authorising body will verify the diligence of the searches.
• Commercial and non-commercial uses of orphan works in the UK will both be permitted, both to maximise the economic potential of proposals and because making a firm distinction between the two is difficult in practice.
• This permission should come at an appropriate price – a market rate, to the extent that one can be established (though the difficulties that may attend establishing that, for example in respect of works not created for publication that are in museums’ collections, are noted).
• This price should be payable in advance (or at agreed times if there is a royalty element) and set aside for any rights holders who may still appear even after a diligent search has not found them.
• Licences will, necessarily, be non-exclusive.
Source: http://www.ipo.gov.uk/response-2011-copyright.pdf