I suppose there could be something about your particular situation that has lead (boom boom) to that cost and advice (?) but generally the supply pipe from the street to your house is your responsibility and you can choose how to deal with it. e.g. if Thames find a leak in it - they inform you and you're obliged to fix it. But it's up to you how you do so entirely. You can ask them to quote; they can provide a range of 'approved companies' to fix it; or you can organise the whole thing yourself. In the case of a leak, Thames used to provide an incentive one-time grant towards the cost of making the repair. Can't remember exactly how much, but it was something like ?125 towards a 'part repair' and a bit more for replacing the whole supply pipe. From memory the quotes for us (from a Thames approved type outfit) were ?450 for a part repair or ?750 to do the whole thing (which for us was a run of maybe 8 or 9 metres from the water box in the street, under a wall, with some concrete work where it came into the house. This was only for the supply pipe from kerbside to front of house though - not replacing all the pipe work once it gets into the house as well, which might have added a bit. As I say, maybe find out if your situation was unusual for some reason.. before blowing your stack!