I'm not in finance either but it seems to me that the issue is that these debts are all in different industries - each industry (I imagine) will have its own standards, hence the credit card companies all behaving in a similar manner.

It's undoubtedly frustrating, and without knowledge of your friend's assets and what he left and to whom, I suspect the best thing to do is to get the property on the market as soon as possible and get it sold so that the estate can pay off the various debts. I think your best bet might also be to get some legal advice from a probate solicitor, as they shoudl be able to give you a steer even if you don't instruct them to deal with the administration of the estate (by the sounds of it, there isn't much money in the estate so it might be a bit too costly to fully instruct solicitors).