Hi this is Westender's daughter. I work for another large gas/electric supplier (not NPower) in the prepayment department. I've spent the last 7 years dealing with problems with prepayment meters, including cards not received.
Firstly please can I ask you not to call 0800 111 999? This is an emergency service for dangerous situations (gas leaks etc) and calling them out for this would be a gross abuse - maybe not quite on the scale of calling an ambulance for a grazed knee but you get the picture. The people on that line have a number of questions to ask - you probably wouldn't be able to get an engineer out anyway but if you did he wouldn't do anything. Those engineers are for fixing dangerous situations, not putting emergency credit on meters.
It is not against the law to leave a household without gas supply, although I do sympathise with the lady concerned. All suppliers have the facility to contact National Grid and request a 'wind-on' (winding the emergency credit on). National Grid will check that certain criteria are met (child under 5 in the premises, person over 65 or somebody with a chronic or long-term heat dependent illness) and then check for availability of their engineers. If they have available manpower they will arrange a non-guaranteed callout with no time-limit. If they say there is no availability then there is nothing that the supplier can do, no matter who the supplier is.
I suggest that you keep calling NPower every few hours as National Grid update their manpower spreadsheets often. If NPower are now closed for the weekend call National Grid yourself on 0845 606 6766, follow the telephone menu and impress on them that your supplier is closed. They should check availability for you.
There is an option to send a company called Accuread to wind your meter on but they don't operate over the whole country. As regards the missing card - it may sound like a cop-out but once again, suppliers are dependent on another company - this time it's the Post Office and we all know how dependable they are.
I really do feel sympathy for the lady without gas - we were left without any heating or hot water here through the really cold snap in January 07 and I have a young daughter - I know how hard it is - but I really do believe that NPower will have done their best for you. We are all human beings working in these big companies and we do, believe it or not, have hearts. I've come home from work before now and fretted all night because I didn't get someone on supply before I left as my mum (Westender) will verify.
I hope the lady gets her gas on soon and can promise that when prepayment meters are working correctly (which they do 99% of the time) they are actually really handy. My company's cheaper though