Buying a whistle is dead easy, and not nearly as traumatic as buying a fiddle, for example. Having said that, there are many different makes available, at many different prices. I have played beautiful whistles which cost in the region of £150, and they sound wonderful. My advice would be not to consider buying any of the more expensive whistles on the market. Your local music shop will have decent whistles for under a fiver, and the chances are it'll be fine for a beginner.

If you need more definite advice, buy an Oak (silver coloured with a black mouthpiece) or an Acorn (painted barrel and a black mouthpiece). The Clarkes Sweetone and Meg whistles are also very good value.

What is important is that you get a D whistle. Whistles come in many keys, but the one most people use to play traditional Scottish or Irish music is a D. The versatility of the instrument is one of its great qualities, and a D whistle allows you to play in D major, E minor, F# minor, G major, A major, A minor and B minor, as well as the modes so common in Scottish and Irish music. You'll probably have to sit out when the fiddles play in B flat, but most fiddles tunes are within the reach of the humble D whistle.