Beaky,
If this is a clause in the contract, I very much doubt they would waiver this for you and alter their policy wording.
I know that RIAS cover this, in addition to a few others but these are mainly for landlords insurances, which wouldn't be applicable. There have been a number of cases where people would leave their homes for more than 60 days to come back to a leaky tap that escalated into severe problems causing extensive damage that could have been nipped in the bud if they caught it in time. This is one of the reasons the clause exists. It's all about minimising the risk.
Try RIAS and let us know how you get on. Bare in mind your existing policy will need to be cancelled.