A few points...
There are faults /customer service people to advise people how to tune in their 'new tv' many people refuse this service as they can't do it or cannot be bothered.
It costs far more than £25 to get a tech to your house to sort it out.
As for the £25 charge for attending a fault with customers equipment I think thats justified also, there are people who refuse to do any diagnosis with you on the phone.
I do think ntl should operate a system like sky, charge a install fee and make the equipment the customers responsibility after 12 months. I'm sure they would be happy to work with the faults guys if they thought they would get charged £70 to fix it.
At the end of the day people complain about anything and On balance free call outs to equipment is not offered by bt nor sky so ntl's service should be dearer as they are offering more.
Go on have a laugh tell your adsl supplier that your modem is faulty
I'm sure they will tell you where you can buy one.