We have heard back from one ADSL customer, who had had problems for a few months with losing his broadband connection whenever someone used the downstairs phone. He appeared to have enough filters in place, and despite spending several hours to technical helplines (on 0845 numbers), they had time and time again blamed something on his PC setup. We sent some replacement filters, and a quick email to us, with a diagram of his system, and we spotted the issue - he had not plugged his phone extension cable into the "PHONE" socket on a filter. Although there was no real need to use our own filters, he was as pleased as punch that we could resolve the issue so quickly.
Oddly, we were the only ones to mention REN on his phone equipment, which had exceeded the recommended REN 3. Still problem solved, and one more happy customer. By the way, we were surprised that our filters are even cheaper than ARGOS sell them for !!
Now all we need is another 100,000 pleased customers, and we could consider retiring !!