If its free for stuff that dating direct normally charges for then I expect ntl have paid for it, if its chargeable as normal this is a money maker for ntl.
These dating sites I have tried datingdirect
and yeah it allows you to search for free but even if you pay then if you send messages to free members they have to signup to recieve your messages so essentially signing up doesnt allow you to send messages to anyone you like but only to other paid up members, I think the free members are there just to boost the numbers but dont really get a service.
I doubt this has any bearing on funds used for other stuff such as upgrades, the costs involved are likely just changing the website and possibility of a fee paid to datingdirect but I bet ntl will get commision for signups originating from their site.