It sounds like you are wanting to buy a used instrument. Why not buy a new one? There are plenty of great stores in the UK. In fact, there are probably more ukulele shops per square mile in the UK than in any other country.
I work for Ohana Ukuleles and our electros are available in a number of shops in the UK e.g. Southern Ukulele Store has only ukuleles and are one of the biggest sellers in the world, Eagle Music has a great range, etc. Check our website, or any other company's website, for details of stores.