Well after yesterday's fiasco i have now had the engineer charge refunded (only had to speak to 5 people to get it sorted!)....
However, the problem with the line is not, and was aparently never a known fault, but something in the house causing the problem... so they need to send an engineer. I have received compo for the time it took to resolve last time, and all calls are now being diverted.... but i have a nasty feeling that they will try to charge for this visit as well