Sounds a bit odd to me. I would suggest that you speak to a couple of local Gas Boiler Installers and maybe the National Grid people now responsible for the gas network.

http://www.nationalgrid.com/uk/Gas/About/

I suspect it would depend on the size of the house. If it were a massive house, with a very large boiler, then there would be certain gas pressure requirements.

Hello I have recently bought house that isn't connected to mains gas.

I spoke to the company that would install the gas for the house and they said that it would cost just over £500 pounds to connect a domestic supply however I might need commercial supply as some five bedroom houses need a large boiler and therefore a larger gas pipe. Any help on what would determine if I need a commercial supply would be appreciated.

Thanks Hugh