Thanks to all for your advice on this one. I as thinking 36v is a bit strange for keeping CMOS data.. :)
Anyway, as you all say the phone should work without this battery, and it is as dead as a doornail, I think I'll have to take it apart and have a look.
My friend thinks it looks like a childs toy phone (it is the bright red one with multicolour buttons) and is quite amused, but I still for some reason really like it.. :)
it is a pity there's no caller ID on these (I don't think it was invented :) ) but other than that....
I'll let you know of any progress once I get it on the bench.
Ray