can i lock my car and leave my dog in boot area

It's never advisable to leave ANY animal in a locked car. It's probably possible, but also possible you'll come back to a dead dog. Did you know that on a 75 degree day, the inside temp in a car can reach over 120 degrees in less than 1/2 an hour.

I will be leaving one of the back windows open with a dog grill so plenty of ventilation will be available

Ask your vet and see what he or she says. Also animal control officer could offer some cogent advice as well.

NO.... It sounds like you want to go to jail for animal cruelty and a broken out window, or both...

its a fair question...but maybe you shouldve added that you'd obviously leave adequate ventilation for your dog which you love very much.!