On Wednesday, 18 November 2015 10:53:13 UTC, Capitol wrote:

It seems that continuity of gas supply is not
assured during this work so someone needs to be present to relight the
boiler after an interruption.

More likely that someone needs to be present to *allow* the boiler to be relit - many residents would not be able to do it themselves. If you left a key with a neighbour they should be able to let the gas contractor in to do this.