Barry,
The 21 Cm band equates to around 1,425 MHz (1.4 GHz). I don't think your current receiver will get within the proverbial bull's roar. To purchase a receiver which covers that frequency could be a wee bit expensive. I have an ancient (now) 'scanner' which in theory covers up to 1.3 GHz. How sensitive and selective such units are at the higher frequencies I do not know.
Incidentally, UHF is generally regarded as those frequencies between 300 MHz and 3000 MHz (3 GHz).
On a general note, the frequency bands are usually grouped in increases of one order of magnitude and start at 3 Hz.
Hang on a bit . . .
See here for the description - it's only terminology/jargon but enables you to be aware of what others are on about.
http://en.wikipedia.org/wiki/Super_high_frequency
Great to see that you are persevering with your project. Please keep us all up to date with your progress.