Expanded polystyrene packaging (Totteridge HP13)

If you are in the High Wycombe area, I would be much obliged for any good-size expanded polystyrene blocks ideally of at least approx 0.6m (2ft) length and 100mm (4") thick, although I can use smaller bits too. Typically these are used in the moulded packaging of large items such as furniture, white goods or other large electrical items and then thrown away. I need to pack out an awkward heavy but in part breakable item in an extra large box. Thanks!