google webmaster tools offers the followng options to set a prefered domain

Display URLs as www.daisydiva.co.uk (for both www.daisydiva.co.uk and daisydiva.co.uk)

Display URLs as daisydiva.co.uk (for both www.daisydiva.co.uk and daisydiva.co.uk)

Don't set an association.

can anyone tell me the best - if any option to use and any benefits or downsides

thank you in advance

Well you need to step back a bit and look at which convention you have been using in your link campaign. Using daisy diva as an example, I would probably set webmaster tools to use www

Which brings up a little problem that I noticed with that site, the non www version of your domain takes the user to a “page can not be displayed” page, I would suggest that you implement a 301 on http://daisydiva.co.uk/ so it resolves to http://www.daisydiva.co.uk/