Thanks for the help Pal, I'm happy that I haven't missed anything important.
Wth regards to your point number 1, about it being illegal to open other peoples mail, I am surprised at this law. Personally, for 2 years, I have been returning his mail unopened "back to sender" for virtually all of these companies, yet the companies seem to ignore that and keep on re-sending them back to my address.
But the one time I open his mail, I discover what he has done - this seems to be when the companies start to take action. As an example, I rang up the Baillifs that are chasing him for unpaid council tax and it seems the only way to stop them sending the same baillif letters again and again is for me to send a utility bill to them as proof of my own residence at the property.
This all seems to make a mockery of the fact it is illegal to open someone elses mail!
Oh well, hopefully my letters will resolve this. I'll be getting my credit reports to see if they have "linked" me to him