Property Advice

Our friend, widowed exactly a year ago, has had to face up to down-sizing, and has sold her farm - house, cottage to be refurbished, several barns and a lot of land. Initially she agreed to allow her English purchasers to move their horses on to the land, put their dogs into one of the barns, and store some items such as equipment and horse boxes. The purchasers having been given an inch seem to have grabbed a mile - they have moved all their belongings into the barns, and have begun taking over the house, even though there are still two weeks to go to the final signing and handing over of keys. Yesterday our friend returned after a day out to find doors and windows wide open in the house, the eight dogs roaming freely through the house, a large section of fencing taken down, and some flowering bushes ripped up - and this on top of taking over a room for an office, and installing and operating their own washing machine without payment for electricity and water. The estate agent won't act, and the Notaire seems unwilling to do anything.
Does anyone know what our friend can do to make the final two weeks in her home less stressful, and reign in the purchasers from a complete take over before the due date?

Are they insured!!! although it isn't uncommen to let people in before the completion date, I'd be very wary about it, certainly don't let them sleep there take up full residence. Unfortunately it's not up to the notaire or the agent to "undo" what I presume is a private agreement between the buyer and seller - did they write down what was allowed/not allowed/was it rather vague? I know that doesn't help resolve the problem, I think she'll either need to put up and shut up for two weeks knowing that it'll all be over very soon (after all, a couple of weeks of hassle and a bit of electricity is a very small price to pay in teh overall situation - especially as many simply can't find a buyer at the moment), or put her foot down and laydown the limits of the pre completion agreement. Bonne chance ;-)