hot water temp fluctuates up and down why???

we have a new gas main put in our road and we were disconnected for a period of time ,unfortunatley we were away on hoilday at time and the company had to come back late one evening to reconnect the supply could this be causing the fluctuation in gas pressure to be causing my water temp flucuations (this was not a problem until the upgraded the pipework)

jason
December 2012