We've spoken to the distributors who have kindly responded:
"...I can confirm that the Lars & Ivan system is available via the independent dealer network and not the national retailers.
It is also true to say that the sales in and out of the Vivanco Dealer Network have been very good indeed, in fact Vivanco are currently very low on stock and waiting for confirmation of their next shipment date. In the meantime I can confirm that Hughes Electrical HQ based at Great Yarmouth have purchased a large quantity. Apart from their 33 high street stores they have a quality on-line business which you can see via http://www.hughesdirect.co.uk/home.php naturally we are not aware of their current stock holding at their stores or the warehouse, however I trust this information will be helpful in responding to consumer enquiries."
So I guess you should try Hughes Direct.