Its highly unlikely that a big name UK bank like Lloyds would go bust because they are so massive, so I wouldnt worry about investing a bigger amount in say a Lloyds regular saver which offers 5.5% on balences over 100k. ING direct is a massive world wide bank, they offer great bonds at the moment. My sisters husband works for them, although they have lost money in the uk its a drop in the ocean compared to their world wide profits.
So far in the crisis no body has lost any money, even with the Northern Rock and Bearns in the US. I still recommend smaller amounts in icesave & kaupthing as they offer great rates. If you lock into fixed rated bonds, many you are unable to cancel them until the term of the bond expires.