Do you think for one minute that Jeremy would be arsing around with phones ? He'd have gone straight in and done the deed in less time it would have taken moving/unplugging phones everywhere.
His interest was money,don't forget ! Not phones,or hiding them under a pile of magazines.
How long do you think the whole process would have taken him ?
What is strange is that he came away without so much as a scratch from Sheila with her long,manicured nails,nor a bruise in this INTENSE struggle with his father in the kitchen. There would also have been cadaver scent in his house,on his person,so the dog which was present outside WHF must have had no sense of smell.