Adjust menu bar text to free space ratio

Hi I need to adjust the menu bar on biketoursforthewounded.co.uk so that it says Challenges rafter than Challenge however when I add the s I get an overflow which creates a second line in the bar and drops the search icon to the second line. Is there a way to reduce the distance between menu headings to allow for the increased heading size without it pushing the search icon on to another line. Hope you can help with this one. Regards Peter