A walk in a Bluebell wood in late April/early May is always a highlight of the wildflower year. Hyacinthoides non-scripta is native to the UK and Ireland, also north-western Portugal and Spain and northern France/Belgium/Holland (and a widely naturalised garden plant). It is probably most prolific in the British Isles and Bluebell woods should be regarded as a national treasure in my opinion. 

 Hitch Wood in Hertfordshire (above) is a particularly good one but there are many others. The presence of H. non-scripta is generally an indicator that the woodland is ancient. There is something almost mystical about walking through the shimmering haze of violet-blue flowers...