I had these when I was a kid and I absolutely loved them so wanted to buy some for my daughter last year but at around a tenner for a set I felt that I could probably find them cheaper somewhere if I waited. Glad I did! Cheapest its been on camelcamelcamel.
£5.49 and free delivery with prime or free delivery when you spend over £10 (non-prime).
They are especially brilliant for homework and projects as you can create brilliant effects and make everything bright and colourful. Great stocking filler!
There is also a set of 6 for £3.95 (no minimum spend).http://www.amazon.co.uk/PENS-ASSORTED-COLOURS-CRAFT-BLOW/dp/B00BRH1OHI/ref=sr_1_13?ie=UTF8&qid=1418334408&sr=8-13&keywords=blo+pens