Some practical problems that no-one really knows the answer to (as far as I am aware) -

Exactly how many tapes Dave Bulmer had
What condition they are in.

What their commercial value is (clearly this is related to the above)
I imagine that the cost of trying to catalogue all the tapes, and in particular assessing their condition and the possible costs of restoring them would be considerable. There is also the considerable problem of trying to establish who is entitled to whatroyalties from the individual tapes. Quite possibly the cost of doing all of this would be far more then their commercial value.

I can't see anyone agreeing to buy all or any of these tapes without this information as they might be buying something worthless.

I don't know what has happened to his business, but I thought it included this
http://www.musicbymail.co.uk/

which has had the same message on it for a very long time.