The problem must be quite recent, as I looked at it not long ago, after reading something on here. Maybe just a temporary website issue, not necessarily defunct.
The Internet Archive has a copy on 14th March. Try the phone. 01792 818414
I've emailed them and had no response - so I am expecting they have closed - hence why I removed the notification for member discount.
You'll also find their Amazon and Ebay store fronts have been closed too.
I wish I'd bought a load more LDS than I did too - at £6 a litre - Citroen had to use 2Lt at £17.34 plus VAT a litre when I had my front strut replaced a few weeks ago.
Please note, I'm no longer active on the Forum, so won't respond to messages.
I think it's just a renaming of the old business as their Amazon page makes reference to NielsenCDG. Their website isn't live yet, I think it's a work in progress at the moment. I have a feeling they changed names around the new financial year - might have been a 'buyout' of the old NielsenCDG name and stock ??
I received an email from Motorply today confirming that they had taken over Nielsen, and offering a 30% discount as a previous customer. Prices still look keen and it seems that everyone gets 10% of their first order.