I bought this not knowing that it is only for heavier doughs, such as wholemeal. I had wanted it to try with white flours and so contacted Lakeland, who kindly refunded the cost.
The other thing I'd point out is that the date stamp, on the pot I was sent, was only a few months ahead: you'd have to make a lot of bread to make the large pot worthwhile.
Update 28/2/2010: Subsequent to the review above I bought two great bread-making books and got the bread baking bug! I hadn't found anyone who wanted the Dough Improver so I thought I would try it and make some brown breads: a multi-grain loaf (which I'd made unsuccessfully in the past) and a honey, sunflower & pumpkin seed loaf. Both turned out very well. I've also tried it with a basically white loaf recipe I've been experimenting with that I substitute 10% of the white flour with spelt wholemeal. Comparing with and without dough improver: the former was better. I've sent a cheque to Lakeland!