Hi there, can anyone help me?

I have six 7 series BMWs, not all on the road but one day. Currently i'm driving an E32 730iSE V8. I've owned it almost two years and it has had this problem since the first day i bought it.
From cold will start first time, every time but when hot, will not turn over until engine has cooled down. Can be anything from 10 minutes or hardly ever in Winter, to up to an hour or more in Summer, 45 minutes tonight. The symptoms are exactly the same as trying to start in gear(inhibitor switch activated). I've been told the inhibitor switch is mounted on the gearbox close to the downpipes so is it this overheating?
Also front PDC sensors stopped working about two weeks after i got it but i've been told the sensors themselves are "clicking", could it be a faulty module?

Please be gentle with me as i'm quite new to this Forum thing. I have no intention of scrapping any of my 7s and will be putting a 1994 740iSE (registered 4th July 1994 with 46000 miles genuine) on the road next month hopefully but funds are tight at the moment.

Thanks in advance.