Another concatenation method I have started using a lot more, especially when building a tooltip, such as on a button, is the join opperator in a filtered transclusion. In many ways its the simplest and cleanest;
{{{ [[string literal]] [{!!fieldname}] [{tiddlername}] [{tiddlername!!fieldname}] [[: ]] [<variablename>] +[join[ ]] }}}
The join does the concatenation and in this case with a blank space between each item.