Hey Ian
Get yourself a cheapo Maycom AR-108 scanner and visit your local airfield, or airport. Listening to Farnborough radar is probably more useful though, as local airfield RT is something you usually pick up quickly, as it's pretty much the same chatter, taxy / joining instructions, circuits etc.
Reading CAP413 is useful. I also found the Pooleys Radiotelephony book (number 7) a great help as it had the RT procedures in visual form and made them more memorable.
Andoni