The problem there is that the values of the LDP, both socially and economically liberal are at odds with some of the nutters, but the LDP is quiet enough on the social stuff that the pretend libertarians can turn off to it
If the two combine, they have to calculate whether the two halves which are more agressively libertarian in one area, can be stronger as a group and not weaker for the shed votes.
Its a danger. The members and core supporters for both parties are more honestly libertarians but I find that a lot of voters only identify with either the economic or more "American" style values, such as laxer gun laws, of the LDP, or the more socially libertarian values of the Sex party.