We put this question to Gigaclear and they replied:
A contract can be taken out by a new owner or tenant at any point, and if there is a straight handover from one to the next then the original customer is not held to his or her contract term, though obviously that is subject to the new owner or tenant taking a new service to replace the original one. The new owner will have to pay a £50 reconnection fee in addition to the service charge (assuming the original customer paid the £100 connection fee).
A customer that has signed up to a service as part of the 30 per cent pre-sales target is expected to honour the order. However, we do recognise that there are some life changing events that cannot be predicted - which include loss of job or moving house, so we do not enforce these orders as there's no point. Equally we hope that people will not place an order they already know they will not be able to honour due to an impending house move.
In short, we are as generous as anyone could expect of us with regard to change of circumstance.”
Which sounds reasonable to us.