Thanks for the replies,
My interpretation of what you said: because the wavelengths are proportional the 2.4 GHz antenna should work, however, because the antennae are not correctly tuned the SWR (Standing wave ratio) may suffer. The means that the maximum amplitude and minimum amplitude may be 'cut off'.
What I might do: get a 2.4 Ghz and 5 GHz dipole and compare them to see how much performance suffers. I'm sure there must be a ham at my university, I badger him for a SWR meter

. I will try and report back with my findings.
Cheers